After debugging a java application that would hang, customer noticed
the only way to get it working again was to restart the desktop.

Checking a forced java coredump the best guess we had was that it
was related to ibus.

Searching the web with some keywords we found that the problem appears
to be fixed if with the environment variable:

IBUS_ENABLE_SYNC_MODE=1

Can you please describe any problems with this setting? At first
it can be assumed that it might run slightly slower, and should be
done only for the java application. Can you confirm it?

What would be the best way to debug this issue, and not need to
use workaround?