I opened up the end away from the servo motor today. I didn't have time to find a bearing ball to do as you described underthetire, but I did measure on the flange and had a look at the bearing on this end. It looks like it's floating because this bearing is a regular NTN 6004Z only secured with a clip. I will measure it properly with a ball later but it looks like it's moving a bit. The bearing was also wet with rust water on this end so this will be replaced as well. If I'm lucky I can get away without replacing the whole screw.
Edit: and yes this part of the machine will get a proper cleanup now! It looks nasty
https://youtu.be/wqutpKMx8DI
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