Powershift upshifting on its own if you hit a bump hard enough?

[Veloo]

Just at the LBS and talking to one of the staff there that had 11 speed silver Centaur on his bike.
He said on more than one occasion, he'd hit a bump on the road hard enough that his drivetrain would end up going up a gear (smaller cog). He pointed the finger at the Powershift lever.

I've ridden Powershift Athena 11 for a bit but have never had that happen to me. Never had it happen on my current Ultrashift either.

Anyone here ever experience it themselves or hear about it?

[dddd]

All slanted-parallelogram rear derailers are affected by bump forces, and unless the spring is stiff enough and the cable also straight and thus stiff enough, auto-shifting can occur in response to abrupt road defects.

But it's usually just momentary, and goes back to the same cog that the chain was on.

Unless that is: 1) the shift lever actuated or slipped or 2) the cabling and/or adjustment was sufficiently poor for the gear selection to be less robust and thus allow a "choice of gears" within any indexed position of the shift lever, wherein the derailer might fail to return accurately and immediately to it chosen gear position (cable friction being a possible factor here).

[raisinberry777]

Haven't had it happen in ~4 years of riding Potenza on the main bike, which uses the same Power shift mechanism.

[DWF]

It doesn’t seem like this should be a product specific, or even a brand specific problem. I experienced this only twice in the past four years. Once on a Campy 8sp drivetrain, and once on a SRAM Red setup. In both cases I concluded the cause to be cable stretch a few weeks after installation leading to the index position drifting off center and mysterious shifting at random times. Sometimes I didn’t even have to hit a bump!

In both cases checking and centering the indexing solved the problem. Cleaning the chain and gunk between cogs helps too.