EPSON ET-4550 doesn't work on the ADF

I suspect if the rollers are worn out they'll need to find a like new set after this long. Preferably from a dead printer which has a low PC and clogged heads, even a bad print mech or some other major failure which is the end of the road. I wouldn't want to pull from a WIC error unit unless the rollers were in perfect shape due to WIC printers usually having a high PC. Clogs are a pain in these so most people dump them once they clog, especially Gen2 and up EcoTank. It's a lot harder to remove the "ink cartridges" once you get to Gen2. At least with these they put a tank on the side and basically made a cartridge block assembly to replace the chipped carts so it's far less difficult but it's still a rough repair due to Epson being sensitive to air in the lines.

Normally it's not worth trying with Inkjets, even these tank based ones. But if OP can get the part for $20 or less it's probably worth a shot. WIC might be fine if the ADF was seldom used but you can do better then picking from the absolute worst faults for a donor part most of the time but you can't tell since Epson completely nukes the printer from operating, even as a scanner.

Reminds me of the C3426 I tried to replace the HVPS and LVPS on which was a loss due to the controller being at fault. Cost me nothing since I pulled them from a money pit.