Since you are about 5 years from current firmware, try updating to see if it fixes the issue. I can't test it since all the test labs are unmanned and everyone has to work from home (My job is/was in a test lab)
Machine is 7855 with firmware 073.040.075.34540 with the office finisher LX. Finisher will not accept custom paper size 7.2 x 14. When the finisher is selected for the output the system ignores the finisher and delivers to the machine output center tray instead.
Have tried loading the paper in by-pass tray and also Tray 1. Same problem.
All specs from Xerox inidicate this finisher will support this paper size. Any suggestions will be appreciated,
Thanks in advance.