We have a Versant 80 with 26 401 on start up
the RAP for this is no help
we have swapped every componet of the registration asy with another machine (all parts are fine)
except for the black glass under the CIS sensor which looks perfect
already cleared all the logs and no codes and still boots up with 26 401
the machine seems to run fine and was able to adjust all the tray registtations without much fuss
026-401 is an informational message that it means when the CIS Side Edge is Out of Range.
You will need a tech to perform DC750 and DC751 in diagnostic mode or even to see on the CSE reports if there are a hidden faults.