A old and with dry conditions 2nd BTR roller will also cause this. Have an Xerox Technician replace it.
The new style Transfer Belt Unit (the one with the cover on the top covering the belt) fixes many issues.
The fault code 394-910 on the Xerox WorkCentre 7220 / 7225 may also display the error message IBT Unit (Transfer Belt Unit) or 2nd BTR (Second Bias Transfer Roller) Unit Not In Position. The error is a hardware issue. Please try removing and reinstalling the identified unit. IBT Unit or 2nd BTR Unit. Power off for 30 seconds and Power back on. If the error message returns a service technician will need to look at the machine to troubleshoot the issue. Please contact your local service provider.