i'm sure some here are familiar with that model, i have a couple of variants of different weights bought as NOS for use on old systems, but all have the same issue of seemingly random movement "twitches" that last roughly a second and seem to appear every 5 to 10 minutes, on average. the mice are clean and are used on a clean surface that does not give such issues with any other mouse. a software issue seems doubtful to me since it happens in both DOS (mouse.com) and win95 alike.

this first appeared like the typical cable wearout symptoms, but i'm not so sure about that anymore after testing several of those. are there any kind of known incompatibilites between older boards and optical PS/2 mice, by chance? the boards i've seen this on so far were all socket 7 with holtek controllers on them.

incidentally also have a logitech M100 that works perfectly fine on 1997 boards, but well, it's USB.