This is important.
Here is an example from the BikeGremlin forum where the information that a SRAM Eagle 12-speed chain was used with an 11-speed cassette was not disclosed from the start, causing confusion and looking in the wrong direction for shifting problem causes:
https://www.bikegremlin.net/threads/trouble-with-rear-cable-pull-ratio.361/post-1585
That is why I'm making this article sticky, and why I wrote this tutorial article (how to help us help you, basically):
Bicycle repair or tuning – how to ask for advice?
- Sticky