is the cross-cutting blade blunt? I could be wrong, but it may be getting resistance as it cuts and then lifts short of completion. or maybe the part that lowers it isnt locking-down properly and is lifting. im just guessing of course.
i would be tempted to switch the machine off completely then separate the cutting head from the print head and operate the cutter head manually to see if it is traveling all the way to lock it down think its only being partly locked down.
if the cable is slightly slack then could cause this or wear on the sheet cut mech. or even a bit sticky.
unfortunately the service command limit adjust also resets the head capping and lock position so needs a lot of care