When you use lambdas inside event classes used in streams it does work in Scala 2.11. It stoped working in Scala 2.12. It does compile but does not process any data and does not throw any exception. I would expect that it would not compile in case I have used some not supported field in event class or I would throw some exception at least.
For more detail check my demonstration repo, please: https://github.com/matej-novotny/flink-lambda-bug