I'd request from the technician he have a specialist come in and get it resolved, if that can't be done call sales about having the finisher swapped out entirely.
If you have a 15 sheet limit, I will assume a Professional Finisher since the Booklet Maker Finisher model does a full 25 Sheets (Uncoated 80GSM), 20 pages from 81-90 GSM, 10 pages from 91-176 GSM. <See Page 21>
If it is taking more than 5 minutes to adjust a fold a specialist would be needed, or finisher replacement. Adjustments should never actually have to be done unless the machine is being run with incorrect stock settings (Think running 176GSM coated paper as 80GSM plain to get the full 15 sheets to run over and over, but if that was the case, the tech would see the damage it caused and wouldn't be trying to fix it with adjustments)
Feel free to PM me your Serial number and Techs name and I will look up service history and see if he has used the internal forums here about any of this. (Assuming you are within North America, I can't view Europe/Asia Pacific Service history)
I guess they just hook their laptop up when they service the machine, it isn't how they make this adjustment. That doesn't alter the fact that this is what happens.
Saying you've never seen that isn't a solution. Apparently the maximum pages the 560 will staple is 15. So, if I do books with 11 pages everything is fine. Then I do books with 15 pages and the fold and stapling is off by a lot, not just a little. The service tech has to adjust it, which takes him more than an hour, more like 2 really. Then it will do the 15 page books. However, if I do an 11 page book, the folding and stapling is completely off the other way. So, the tech has to re-adjust the machine back the way it was. It's absurd. They have had to do this a half dozen times already. I doubt changing a roller is going to fix it.
Not sure why he is going out and hooking up a laptop at all honestly.
Fold position is adjustable by anyone directly on the machine, no need of a laptop or tech for it.
Machine Status > Tools > System Settings > Common Service Settings > Maintenance > Finisher Adjustment > Adjust fold position.
That said, 10 mm is absolutely massive for a shift, I have never seen any printer shift a fold that far, that would imply a serious issue in the rollers or a really incorrect paper stock setting on the device.
I have a 560 with the booklet maker finisher. It has a serious problem with folding and stapling. When we do booklets that have ~ 10 sheets 11x17 that are folded and stapled (all sheets are 20# copy paper), there is no problem. Then when we do a booklet that is identical, but has 15 sheets, the folding and stapling are off center about 10mm. Every time we do this job, about once a year, the service tech has to come out and adjust the fold and staple, by hooking his laptop up to the machine. Then, once this job is done, he has to come back, and adjust it back the way it was before, or it will fold and staple off when we do fewer sheets.
It seems crazy the service tech has to do this every time, but I guess the machine can't make that adjustment.
thanks for the help!