Github user NicoK commented on the issue:
https://github.com/apache/flink/pull/6272
actually, I forgot to adapt the unit test which relied on the previous
order of the calls and assumed that the buffer got recycled. With the changes
from the fixup, the buffer is not recycled by the failure directly but rather
during error handling which will eventually release the channel's resources.
-> this is now fixed as well---
