Unable to Save selection of 'Add People'/'Add Group' in 'flowable-task'

I can’t save selected people in ‘flowable-task’, I marked this field is mandatory one.

I use latest flowable-allinone docker image with default H2 DB.
Any ideas about this?

One more information is that this only existed in 6.4.2 and above docker images.
It works well in version 6.4.1.

Is there any stacktrace?

Can you share more information about the process/form you are using?