|608ZZ bearing and PLA tire/washer|
After installing the tires, the observable backlash is reduced to less than 1 mm, hopefully fixing the problem.
|Bearings with tires installed on centre block|
The STL for the tire is here, it takes about 1 gram of filament, and 5 minutes to print one at 0.2mm layer height with a 0.4mm nozzle. As for installing them, you need to apply even pressure across the entire rim or the part will snap, so I'd recommend printing a few extras. Overall, probably one of the simplest fixes to a problem I've made so far.