Attack this in stages. Fill the unit with water only, and bring it to temp. Check the temps. Too hot could soften coating and lead to scratches on otherwise good racks and transfer guides. If the unit is cruddy it could be crud in a spray bar of chems that is scratching; check that there are filters in the machine, and that they are functional. Running for a few days while it is chewing though dilute toillet bowl cleaner will dislodge crud you never knew was caked in different spots. Spray and wipe clean. Then rinse, rinse and rinse.
I suspect that you might will find a caked in piece of tar on the cloth terry lower developer roller cover that could be the scratcher. These things pick up chunks of oxidized developer and only a full tear down can get this rack really clean. I did one once, and it was about 1.5 hours each way with a soak of the terry thing off the roll for a day in between, but mine was in truly disgusting shape.
With the lid off, remove transfer racks, and feed the test paper in one tank at a time, ruling out the tank racks one by one as being a potential source of the problem.
Then add one transfer guide at a time, and try the paper path two tanks in a row to test out transfer guides one at a time once the tanks have testsed scratch free.
The next step is to test infeed mechanisms. There are mechanical fingers that sense for determining replenishment rates on the intake- they could be a source of your problems as well.
If all tanks look good, than look to the dryer. Here it could be a challenge to figure out if there is a hot spot on one heater that is locally softenting the coating, leaving it suceptible to subsequent damage on a final rack, or if one fan has konked out.
You are in a way are fortunate that ALL material comes out of this processor scratched. Finding intermittent defects is what really drives me nuts.
For good measure after a long period of inactivity, I will sometimes send a sheet of long unserviceable ep/2 paper though full width to pick up any munge clinging to rollers, etc.
Then I send it though upside down if it came through clean right side up just to make sure that things are tidy.
There are things called clean out sheets that do this on one pass, singe they are gelatine coated on each side.
Good luck with your detective work.