Indexing Issue: Shimano 105 R7000 Only Shifts 9 of 11 Speeds — What Am I Missing?

Hello everyone,

I’m having trouble with my Shimano 105 R7000 rear derailleur. During a recent ride, I seemingly lost access to some of my gears. In the video I filmed, the first two shift clicks don’t actually move the chain, but even counting those, I only get nine clicks total instead of the expected eleven.

If I crank up the cable tension so that the first two shift clicks work going to larger cogs, they then fail on the downshift side—I can’t shift back to the smaller cogs. I’ve already backed off both H- and L-limit screws completely to ensure they aren’t stopping the cage.

I’m not sure whether the culprit is cable issue, or if it’s an issue with the shifter itself. Has anyone run into this? Any diagnostic steps or fixes I should try before replacing parts? Thanks in advance for your guidance!

PS: I also have an unrelated front derailleur issue, link in the comments.