During the release of Flink 1.7, the value of AvroSerializer, serialVersionUID was uptick to 2L (was 1L before).
Although the AvroSerializer (along with it's snapshot class) was migrated to the new serialization abstraction (hence free of Java serialization), there were composite serializers that were not yet migrated during that release (i.e. StreamElementSerializer), and were serialized with Java serialization into the checkpoint/savepoint.
In case that one of the nested serializers were the AvroSerializer we would
bump into deserialization exception due to a wrong serialVersionUID.
This issue was initially reported on the user mailing list: