Outlook forms get deleted regularly

Hi

I made a change to the Desktop Policy for a customer (Advanced > Outlook > Deploy forms locally > Delete) for a test.
Policy is changed back to "Always" now but i got feedbacks from users that forms still are missing in Outlook.

The problem occurs only to a subset of Users within the same provisioning group.

Synchronizing a selected Mailbox for an affected User via Archiving task has the effect that forms are redeployed after restarting Outlook.

Problem is, after scheduled Archiving task has run (2x a day) on Vault Server, forms get deleted again.
I successfully have tested that 2 times, EV Log presents following line:

02/05/2018 11:39:36.653[10900][H]: Deleted EV form: IPM.Note.EnterpriseVault.PendingArchive.ArchiveMe (V11.0.1-001) from Personal Form Library due to Desktop Policy value

Desktop policy for the provisioning group is set to Deploy always...

It seems to me that there is a inconsistency in applying Desktop Policy between manual sync and the scheduled sync after which forms get deleted from the personal form store.

An Update to a newer Addin hasn't been successfull.

Enterprise Vault is Version 12.1.0.1424
AddIn Version 11.0.1.3683 (current) / 12.1.2.1531 (test with updated version) on Outlook 2013.
Exchange is Version 2013

Any suggestions? Hints? Anything?