“Someone capitalized the first letter of every word in a sentence”.

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.

My first thought on anything like that is always to redo an indexing but also make sure the B screw is set properly, because that can causes so many shifting issues.

The odd part, and what I don’t fully understand here, is that it seems to work as a 10 speed? Am I understanding that properly? 9 clicks plus initial position?