beam_PostCommit_Java_Nexmark_Flink are failing continuously

[Boyuan Zhang]

Hey team,

beam_PostCommit_Java_Nexmark_Flink
<https://builds.apache.org/job/beam_PostCommit_Java_Nexmark_Flink/>  test
target has failed for a long time. Is this something expected? If not, any
insights on these failures?

Boyuan