The scroll wheel began “slipping”. model TR0006.
Previous versions of this mouse used an optical encoder, and the guidance was to clean it. The one I have, however, has a 3-pin device marked Kailh and the number 8.
by the cyan shaft it seems closest to kailh’s EN98 series, specifically CEN988012R21.
digikey has a simliar component from Alps, but they only come in 7 or 9 mm, no 8 mm.
I’m told TTC Gold is a good brand. Many on eBay, but came to same price as this german vendor https://www.bananas-gaming.com/. Ordered one “8 mm TTC Gold (Dustproof)”.