KryoSerializer random exception

java.lang.Exception: The data preparation for task 'CHAIN GroupReduce (GroupReduce at createResult(IndexMappingExecutor.java:42)) -> Map (Map at main(Jsonizer.java:128))' , caused an error: Error obtaining the sorted input: Thread 'SortMerger spilling thread' terminated due to an exception: Unable to find class: java.ttil.HashSet
        at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:456)
        at org.apache.flink.runtime.operators.BatchTask.invoke(BatchTask.java:345)
        at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.RuntimeException: Error obtaining the sorted input: Thread 'SortMerger spilling thread' terminated due to an exception: Unable to find class: java.ttil.HashSet
        at org.apache.flink.runtime.operators.sort.UnilateralSortMerger.getIterator(UnilateralSortMerger.java:619)
        at org.apache.flink.runtime.operators.BatchTask.getInput(BatchTask.java:1079)
        at org.apache.flink.runtime.operators.GroupReduceDriver.prepare(GroupReduceDriver.java:94)
        at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:450)
        ... 3 more
Caused by: java.io.IOException: Thread 'SortMerger spilling thread' terminated due to an exception: Unable to find class: java.ttil.HashSet
        at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$ThreadBase.run(UnilateralSortMerger.java:800)
Caused by: com.esotericsoftware.kryo.KryoException: Unable to find class: java.ttil.HashSet
        at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:138)
        at com.esotericsoftware.kryo.util.DefaultClassResolver.readClass(DefaultClassResolver.java:115)
        at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:641)
        at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:752)
        at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:143)
        at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:21)
        at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:761)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:228)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:242)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.copy(KryoSerializer.java:252)
        at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.copy(PojoSerializer.java:556)
        at org.apache.flink.api.java.typeutils.runtime.TupleSerializerBase.copy(TupleSerializerBase.java:75)
        at org.apache.flink.runtime.operators.sort.NormalizedKeySorter.writeToOutput(NormalizedKeySorter.java:499)
        at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$SpillingThread.go(UnilateralSortMerger.java:1344)
        at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$ThreadBase.run(UnilateralSortMerger.java:796)
Caused by: java.lang.ClassNotFoundException: java.ttil.HashSet
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:348)
        at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:136)

Caused by: java.io.IOException: Serializer consumed more bytes than the record had. This indicates broken serialization. If you are using custom serialization types (Value or Writable), check their serialization methods. If you are using a Kryo-serialized type, check the corresponding Kryo serializer.
    at org.apache.flink.runtime.io.network.api.serialization.SpillingAdaptiveSpanningRecordDeserializer.getNextRecord(SpillingAdaptiveSpanningRecordDeserializer.java:142)
    at org.apache.flink.runtime.io.network.api.reader.AbstractRecordReader.getNextRecord(AbstractRecordReader.java:65)
    at org.apache.flink.runtime.io.network.api.reader.MutableRecordReader.next(MutableRecordReader.java:34)
    at org.apache.flink.runtime.operators.util.ReaderIterator.next(ReaderIterator.java:73)
    at org.apache.flink.runtime.operators.FlatMapDriver.run(FlatMapDriver.java:101)
    at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:480)
    at org.apache.flink.runtime.operators.BatchTask.invoke(BatchTask.java:345)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ArrayIndexOutOfBoundsException: -2
    at java.util.ArrayList.elementData(ArrayList.java:418)
    at java.util.ArrayList.get(ArrayList.java:431)
    at com.esotericsoftware.kryo.util.MapReferenceResolver.getReadObject(MapReferenceResolver.java:42)
    at com.esotericsoftware.kryo.Kryo.readReferenceOrNull(Kryo.java:805)
    at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:759)
    at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:228)
    at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.deserialize(PojoSerializer.java:431)
    at org.apache.flink.api.java.typeutils.runtime.TupleSerializer.deserialize(TupleSerializer.java:135)
    at org.apache.flink.api.java.typeutils.runtime.TupleSerializer.deserialize(TupleSerializer.java:30)
    at org.apache.flink.runtime.plugable.NonReusingDeserializationDelegate.read(NonReusingDeserializationDelegate.java:55)
    at org.apache.flink.runtime.io.network.api.serialization.SpillingAdaptiveSpanningRecordDeserializer.getNextRecord(SpillingAdaptiveSpanningRecordDeserializer.java:124)

java.lang.RuntimeException: Cannot instantiate class.
	at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.deserialize(PojoSerializer.java:407)
	at org.apache.flink.runtime.plugable.NonReusingDeserializationDelegate.read(NonReusingDeserializationDelegate.java:55)
	at org.apache.flink.runtime.io.network.api.serialization.SpillingAdaptiveSpanningRecordDeserializer.getNextRecord(SpillingAdaptiveSpanningRecordDeserializer.java:124)
	at org.apache.flink.runtime.io.network.api.reader.AbstractRecordReader.getNextRecord(AbstractRecordReader.java:65)
	at org.apache.flink.runtime.io.network.api.reader.MutableRecordReader.next(MutableRecordReader.java:34)
	at org.apache.flink.runtime.operators.util.ReaderIterator.next(ReaderIterator.java:73)
	at org.apache.flink.runtime.operators.FlatMapDriver.run(FlatMapDriver.java:101)
	at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:480)
	at org.apache.flink.runtime.operators.BatchTask.invoke(BatchTask.java:345)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: it.okkam.flink.test.model.pojo.VdhicleEvent
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:348)
	at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.deserialize(PojoSerializer.java:405)
	... 10 more

com.esotericsoftware.kryo.KryoException: Unable to find class: ^Z^A
        at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:138)
        at com.esotericsoftware.kryo.util.DefaultClassResolver.readClass(DefaultClassResolver.java:115)
        at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:641)
        at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:752)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:228)
        at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.deserialize(PojoSerializer.java:431)
        at org.apache.flink.runtime.plugable.NonReusingDeserializationDelegate.read(NonReusingDeserializationDelegate.java:55)
        at org.apache.flink.runtime.io.network.api.serialization.SpillingAdaptiveSpanningRecordDeserializer.getNextRecord(SpillingAdaptiveSpanningRecordDeserializer.java:124)
        at org.apache.flink.runtime.io.network.api.reader.AbstractRecordReader.getNextRecord(AbstractRecordReader.java:65)
        at org.apache.flink.runtime.io.network.api.reader.MutableRecordReader.next(MutableRecordReader.java:34)
        at org.apache.flink.runtime.operators.util.ReaderIterator.next(ReaderIterator.java:73)
        at org.apache.flink.runtime.operators.MapDriver.run(MapDriver.java:96)
        at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:480)
        at org.apache.flink.runtime.operators.BatchTask.invoke(BatchTask.java:345)
        at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
        at java.lang.Thread.run(Thread.java:745)

Caused by: java.lang.ArrayIndexOutOfBoundsException: -2
	at java.util.ArrayList.elementData(ArrayList.java:418)
	at java.util.ArrayList.get(ArrayList.java:431)
	at com.esotericsoftware.kryo.util.MapReferenceResolver.getReadObject(MapReferenceResolver.java:42)
	at com.esotericsoftware.kryo.Kryo.readReferenceOrNull(Kryo.java:805)
	at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:759)
	at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:135)
	at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:21)
	at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:761)
	at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:232)
	at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.deserialize(PojoSerializer.java:431)
	at org.apache.flink.api.java.typeutils.runtime.TupleSerializer.deserialize(TupleSerializer.java:135)
	at org.apache.flink.api.java.typeutils.runtime.TupleSerializer.deserialize(TupleSerializer.java:30)
	at org.apache.flink.runtime.io.disk.ChannelReaderInputViewIterator.next(ChannelReaderInputViewIterator.java:100)
	at org.apache.flink.runtime.operators.sort.MergeIterator$HeadStream.nextHead(MergeIterator.java:161)
	at org.apache.flink.runtime.operators.sort.MergeIterator.next(MergeIterator.java:113)
	at org.apache.flink.runtime.operators.util.metrics.CountingMutableObjectIterator.next(CountingMutableObjectIterator.java:45)
	at org.apache.flink.runtime.util.NonReusingKeyGroupedIterator.advanceToNext(NonReusingKeyGroupedIterator.java:130)
	at org.apache.flink.runtime.util.NonReusingKeyGroupedIterator.access$300(NonReusingKeyGroupedIterator.java:32)
	at org.apache.flink.runtime.util.NonReusingKeyGroupedIterator$ValuesIterator.next(NonReusingKeyGroupedIterator.java:192)
	at org.okkam.entitons.mapping.flink.IndexMappingExecutor$TupleToEntitonJsonNode.reduce(IndexMappingExecutor.java:64)
	at org.apache.flink.runtime.operators.GroupReduceDriver.run(GroupReduceDriver.java:131)
	at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:486)
	at org.apache.flink.runtime.operators.BatchTask.invoke(BatchTask.java:351)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:584)
	at java.lang.Thread.run(Thread.java:745)