Between 1994 and 1996 Shimano seemed determined to set a definitive low point so that whenever anything went wrong with componentry they made after that they could say,"yeah, well at least it's not as bad as THIS crap."
Usually what snaps is the cheesy gear indicator. Several models of Shimano shifter had cheesy indicators that year, all prone to failure.
The shifter mounting tabs on the levers push the shifter pods into the rise handlebar, restricting them to a fairly steep angle. The plastic is so cheap that the nozzle broke off the right shifter, so I had to fabricate a metal ferrule into which to insert the cable housing. I cut a Schrader valve cap and pressed it onto the old adjuster I ground down to use as the ferrule. When I tried to use the adjuster full length, to provide convenient cable adjustment at the shifter and not just the derailleur, the threaded shaft of it jammed the shifter mechanism. Ground down, it made a more substantial ferrule than any of the others I had in my parts farm.
Purveyors of technology would ask, "why are you still running this crap? Buy our new stuff." It's not built to last. It's built to be replaced regularly. Hell, some of it isn't even built to be USED.
The M290 crank that went with this gruppo originally is one of the trio of "Cranks of Death" from the great recall of 1997. The others are the CT 90 Altus and the MC 12 Alivio. A few are still roaming around out there after all these years. We have treated two or three this summer. Cranks of Death is just a pet name. No actual deaths have been attributed to these cranks, only injuries including fractures.
A couple of years ago I had already replaced the original Crank of Death on this bike with a nice replaceable-chainring model and done a comprehensive tune up. Aside from the position change I had to de-earwax the shifters and pump up the tires. Those are on the verge of dry rot. I'll tell the owner to ride a lot to get full use out of the tread before the tire casing disintegrates. Maybe do some skids.