What can literally happen when your mechanic replaces your close to 3/4 stretch 11spd shimano chain with a same brand 10spd chain, on your 11spd set of Ultegra R8000 components?
SMN CN-HG95 116L 10SP CHAIN SIL-TEC ?


This happened to me in one of my service tune-ups (replacing an old chain).
The results were not pretty. I rode with it for about 3 weeks, including a trek up Waimea Canyon on Kauai.

Before I embellish, I would like to know what *could* happen if the above was done by a "trusted bike shop mechanic"

I appreciate your feedback