Here’s a simple fix that made a big difference. The slightest amount of resistance caused the keyboard rollers to stop. Even the normal action of depressing a key could cause drag, and it was necessary to give the rubber roll shaft gear a bit of a push to keep things rolling.
After tapping out the collar pin, I gave the friction spring and shaft pulley a splash of white gas and a good scrubbing. Then I carefully bent the spring to give it a bit more tension against the pulley. Much better.