Event 3479 Could not add all the mailboxes to the processing queue

we have EV 11.0.1. CHF2 

since a few days if the exchange Mailbox archiving Task is starting we get following message in the event viewer:

EVENT 3479

Could not add all the mailboxes to the processing queue. The mailboxes that could not be added to the queue will be processed on the next run of the archiving task.

Mailboxes added to queue: 0 of 1154
MSMQ name: DIRECT=OS:SW-xxxxx-xxxxx\Private$\Enterprise Vault Exchange Mailbox Task for SW-xxxxxx-xxxxx 161109073116 A5
Run ID: Scheduled_20161109_074803
Exchange Server: SW-xxxxxx-xxxxxx
Task name: Exchange Mailbox Archiving Task for SW-xxxxxx-xxxxxx

so at the end NO Mailboxes are add the the queue. If i look in the Report i can see it is "running" but nothing happens.

next day same Message same result.
If i try to do a run now with a single Mailbox it will run successfull
if i try to do a run now with more then one Mailboxes i can see every second a new report entry and come, ends and start again... in a neverending loop.
Only clear the MSMQ queue solve this.

If it try to do a run now with "All Mailboxes"  i have the same result as with the normal scheduled run.

I tried to delete the queues.  same result as before

I tried to delete the Mailbox Task and define a new one. Same result as before

I have done no changes in EV, and the Exchange Guys told me they also have made no changes

any ideas?

Thanks 

Kai