Printer not working | Delay spool 追蹤

Experts,

we have upgraded to Bartender 2016 R4 (from 10.1) (Automation version)

We are printing from SAP (creating a trigger file to a network drive), then printing this file with Integration Builder 

Since the upgrade, we are facing problems - Bartender is saying label is spooled, I can check the spooler of the printer and can see a lot of open spool request, first one "Printed", rest is "Waiting".

After a few minutes, all labels are printed (could take more than 10 minutes). With the old version, this was really online, without any delay!

We already checked virus scanner, network, deleted the printer and recreated it, ... without any success!

If we deactivate database (print into database for history explorer), printing is working better, but as well not smooth

Any ideas what we need to check?

Thanks

Michael 

PS our database was online for 14 hours - database size was 1,5 GB, log file of database alsmost 5 GB?