FileVault enabled accounts not shown on login screen

Hi everybody,

with some of our iMacs (all 14 of them are set up the same way) we have the following problem: When a new mobile network account is created (1st: create a network account on the OS X Server in its Open Directory database, then network user folder synced to local user folder on iMac) and this particular account is enabled to handle FileVault encryption of the local hard drive in „System Preferences“ -> „Security & Privacy“ -> „FileVault“ and even the output of

sudo fdesetup list

lists this special account, the user is not shown at the very first login screen (light gray). I deleted the local user and re-synced, I removed the account from the list of FileVault users and re-enabled the account - all to no avail.

Now I disable FileVault completely and will re-enable it later. That lasts hours…

Is there any more convenient way to fix this? May the „sync“ command of fdesetup be an option?

Hope, someone knows the answer or may even give me a hint.

Best regards from Hamburg

Olaf