When printing to printers with V-Layer feature the print job get’s stuck in status “spooling”.
Tracking / Job statistics is enabled but not configured.
In Event Viewer a message was posted “TPTrackSvc: Database connection failure detected, connection process suspended…”
ThinPrint Engine (any version)
Disable/ Tracking and set Job statistics update speed to “off”. Go to the ThinPrint Engine Configuration -> Tracking set to OFF