TL;DR: This won't last long, but it'll get you back in the game while you get bearings for your AMS Internal Hub Unit.

This bushing is sized to fit OVER THE INSIDE RACE of the bearing. The inside race stayed on firmly in my case, and was not easy to pry off by hand without damaging the roller.

I got nowhere with Bambu support when I got the error in the attached image: "Unable to feed filament into the extruder. This could be due to an entangled filament or a stuck spool. If not, please check if the AMS PTFE tube is connected"

Well of course neither of those things were actually the problem. It turns out the odometer on the internal hub unit (see pics) wasn't able to spin freely. If you depress the spring and push out the pin holding the presser arm in place, you can get at the two bearings on the odometer shaft. One of mine had exploded, preventing smooth operation. The odometer would therefore jam, and the printer would generate the above error.

While I wait for a replacement internal hub (in intend to make it a backup) and replacement bearings, I whipped up a sacrificial bushing to allow the odometer to spin while I make Halloween decorations. I have no idea how long it will last, but hopefully long enough to get new bearings.