Github user NicoK commented on the issue:
https://github.com/apache/flink/pull/5557
While this may certainly "fix" the problem with the flush-always setting, I
don't like the approach of ignoring the problem that some `notifyDataAvailable`
calls are ignored and we have to wait for the next flush to appear. We should
rather fix the cause and not hide the problem (we currently have no test that
shows the problem!).---
