Error in restoring checkpoint/savepoint when Flink is upgraded from 1.9 to 1.10.2

1) Trying to restore saved savepoint of Flink 1.9 in version 1.10.2 resulted in the below error.

Could not restore keyed state backend for WindowOperator_306d8342cb5b2ad8b53f1be57f65bee8(1/4) from any of the 1 provided restore options._

Complete Stack Trace :
2020-12-04 15:17:21 java.lang.Exception: Exception while creating StreamOperatorStateContext. at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:191) at org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:255) at org.apache.flink.streaming.runtime.tasks.StreamTask.initializeStateAndOpen(StreamTask.java:989) at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$beforeInvoke$0(StreamTask.java:453) at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$SynchronizedStreamTaskActionExecutor.runThrowing(StreamTaskActionExecutor.java:94) at org.apache.flink.streaming.runtime.tasks.StreamTask.beforeInvoke(StreamTask.java:448) at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:460) at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:708) at org.apache.flink.runtime.taskmanager.Task.run(Task.java:533) at java.lang.Thread.run(Thread.java:748) Caused by: org.apache.flink.util.FlinkException: Could not restore keyed state backend for WindowOperator_306d8342cb5b2ad8b53f1be57f65bee8_(1/4) from any of the 1 provided restore options. at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:135) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:304) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:131) ... 9 more Caused by: org.apache.flink.runtime.state.BackendBuildingException: Failed when trying to restore heap backend at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.build(HeapKeyedStateBackendBuilder.java:116) at org.apache.flink.runtime.state.filesystem.FsStateBackend.createKeyedStateBackend(FsStateBackend.java:529) at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.lambda$keyedStatedBackend$1(StreamTaskStateInitializerImpl.java:288) at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:142) at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:121) ... 11 more Caused by: java.lang.IllegalStateException: Unexpected key-group in restore. at org.apache.flink.util.Preconditions.checkState(Preconditions.java:195) at org.apache.flink.runtime.state.heap.HeapRestoreOperation.readStateHandleStateData(HeapRestoreOperation.java:248) at org.apache.flink.runtime.state.heap.HeapRestoreOperation.restore(HeapRestoreOperation.java:154) at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.build(HeapKeyedStateBa
ckendBuilder.java:114) ... 15 more

Earlier tried restoring the 1.9 savepoint in 1.11.2 and it was failure with the error specified in the Bug ID. That bug is still in unresolved state.
https://issues.apache.org/jira/browse/FLINK-20376