TimSort throws "Comparison method violates its general contract!" error using NaturalStringComparator.
This was confirmed by unit testing against a source code of 6.14.2.
Add a following testing method against test class for NaturalStringComparator
No exception raised and sorted correctly.
Test fails with following Exception.
This was confirmed by unit testing in my end, however a customer faced this error in page tree sorting.
Adding this JVM system property fixes the issue: