Hi,
Can you please enable additional log level in data-va and re-do the same use case?
In /opt/zimbra/conf/log4j.properties.in , add the line - log4j.logger.hzndata.auth=TRACE at the end.
Then, restart the data server using the following commands:
su - zimbra
zmcontrol restart
Then, send us the mailbox.log from /opt/zimbra/log folder.