pyspark.sql nondeterministic issue with row fields

The following issue happens only when running pyspark in the python interpreter, it works correctly with spark-submit.

Reading two json files containing objects with a different structure leads sometimes to the definition of wrong Rows, where the fields of a file are used for the other one.

I was able to write a sample code that reproduce this issue one out of three times; the code snippet is available at the following link, together with some (very simple) data samples:

https://gist.github.com/armisael/e08bb4567d0a11efe2db