Good afternoon

We're using ZCM 10.2.2 with the ZAM module activated. We're in the process of importing purchase records from standardized txt file (based on the official Novell Excel sheet).
However, there are days where we're simply unable to import anything. No errors occur. Neither on the 'Import Status' page nor on 'Configuration\System Information'.
Sometimes after a Server Reboot it starts working again, sometimes it doesn't.

Help is greatly appreciated.