i think you should follow the normal gerber evaluation routine we always use
blow out with compressed air
reseat all the plugs and connectors
(if you want to scrub the circuit boards with alcohol and perhaps resolder all the HEAVIER jack connectors on circuit boards
look for "ringed" solder connections on circuit boards
(i have used this process with gerber gs & gx plotters for 35 years)
since there is an encoder motor error figure out which motor that error refers to closely examine connectors, be sure the motor doesn't need a "tap" with the rubber hammer to free up a misaligned bearing
is this one of the motors where you need to open, remove the circuit board and clean the little ceramin encoder disk?
FORGIVE THE SHOTGUN APPROACH TO YOUR PROBLEM, but it often works with all the other gerber products
Joseph gerber was a genius, but he was a "one trick pony" all his equpment was very similar to the point that if you had any
gerber experience you could often fix a piece that you weren't experienced enough to load media in