So I got some strange shifting issues with my 105 road shifters (ST-R7020) combined with GRX derailleur (RD-RX812). The cassette is deore CS-M5100-11
Now in theory, and according to Shimano's compatibility chart this should be compatible configuration, despite a little mix-and-match
https://productinfo.shimano.com/en/compatibility/C-454
Now the problems I have screams still for compatibility issues with slightly wrong pull ratios
Going from smallest cog to largest, the first 4 cogs are shifting perfectly. Then the next couple clicks want to over shift and skip cogs, and the largest 3 are shifting perfectly again. In total it takes 9 clicks to go through the 11sp cassette. What fucks my mind over, is the top and bottom cogs that shift perfectly, if the pull ratio was wrong, these would have equal problems?
I would check the user manual of the derailleur for the cable routing out the derailleur. I don't remember which RD it was, but I installed one on a friend's (gravel) bike, and my dumbass thinking I knew better didn't read the manual and installed as usual, but that specific RD wanted an "odd" route for its cable. I didn't know that because I didn't read, so the friend had bad shifting in the middle of the cassette until I read how I was supposed to do it.
I wouldn't be surprised if a pro missed it because it was a really unusually tight route, and actually doing it solved the unpleasant shifting, even if it's a little unsettling to look at.
Thanks for the reply. I'll have a look at some documentation and compare to see if I can improve it!