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sluggish Logitech Trackman Marble T-BC21 - bearings/trackball wear?

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I'm hoping people can shed some light on this all for me please.

I really, really thought one of my Marbles had finally died, from an optical sensor failure or its circuitry failing. Symptoms were that the ball moved (or I thought it did?) but the cursor only moved intermittently. I tried it on two machines, one Linux, one Windows 10. It was like this for a while. Having taken it apart it I randomly noticed it is now working again. No idea why. But...

The ball is very sluggish, about 1/3rd of the travel of the other one I have. It only travels a screen width at best, which makes it a bit of a pain. It is also noisier. Both Marbles are well-used and I have completely lost track of how many miles each has done. No gaming, just alot of office work over the years. No lubrications added AFAIK. If I swap the balls over, the bad Marble is a bit better and the good one is a bit worse. This implies it is somehow related to the ball as oppose to solely the white bearings.

I've tried cleaning the ball with soap and water. Also tried using leather on the white bearings to free them if stuck, and using white spirit (no isopropyl alcolhol/surgical spirits in the house) to free them up. No noticeable change.

Using a magnifying glass I can't see any difference between the surfaces of the trackballs, except the bad one does appear a bit less reflective. A light reflected in it is less bright and the edges of the image are a bit less sharp. But it's subtle. I can't tell if the white bearings are rotating, jammed or have flat spots, they are too small even with a magnifying glass. They look like the good Marble's. I don't think any have "sunk" (as reported in (ref 1)).

Ref 2 reports a similar issue to mine, apparently without remedy. There, hugeaurorafan thinks that the white bearings don't wear and the sluggishness is from the trackball getting scratched.

I am thinking I need to get the trackballs under a microscope and look for surface damage/scratches being worse on the the bad one. I'd like to see the condition of the white bearings, which also needs a microscope. I'm not sure how to remove them, I've tried and they appear too tight. I wonder if they are bonded in and aren't designed to move. In ref 1, ianisthewalrus advises drilling a small hole behind the bearings to allow a needle to push the bearing out from behind. That might work. I'd then be able to inspect them and measure the diameter. If I don't lose the tiny things.

If the trackball surface is the problem, I don't have a remedy, can you polish whatever resin it is made from? ArchieEU in Ref 3 recommends car headlight polishing paste and others advise on other polishing compounds. I might be able to source new bearings if the diameter matches up, but I'll have to guess at material if there are any options at all.

I'd be most grateful for any advice, experiences. I kind of love these workhorses. Logitech must be losing their marbles to stop making these Marbles. Sorry  :D.

ref 1:
ref 2:
ref 3:

My Logitech "alien hand" trackball (which identifies as a Marble Mouse by USB ID) does that every now and then.  It has always been just a hair or a bit of fluff on the window of the optical sensor.

~15 years+ old now, and 8-10 hours of use per day, 7 days a week.

Yes, regarding the (for now vanished) problem of intermittent cursor, fluff/hair that would usually be the cause. It appears there are lots of people who have used Marble Mouses for a very long time indeed, it'd be nice to know if/what wear is making this particular one sluggish. I am wondering if there is a feedback that accelerates wear: it gets harder for fingers to move it due to sluggishness => you have to press down harder to get it to move (less "spin" more "move") => accelerated wear on ball/bearings. My partner uses it so it's hard to judge if they've had to do that.

What's the "Alien hand" trackball? I'm currently trialling a Mouse-Trak Industrial, which seems anachronistic - but might be the future as well.

"Alien Hand" is a snide reference to some of Logitech's annoying advertising, years ago.  The "Marble Mouse" version I have is the symmetrical, just-as-uncomfortable-with-either-hand model, not one of the right-hand-only versions.

Mine doesn't have bearings; the ball rides on three tiny plastic pegs. They're still as tall as they are around, so I'm guessing wear has been minimal so far.

Ah, that passed me by at the time. I see what you mean, I found it on the Xah Lee website just now. The Marble Mouse you describe sounds like my T-BC21 and I really like them a lot until this one got sluggish. But I just got lucky with them, first trackball I tried, decades ago. I occasionally use a mouse with a scroll wheel and I do like that. The attached shows what I call a bearing on a T-BC21, no idea if they are supposed to rotate, or if they actually do.


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