Moving right analog stick inteferes with the left.
Just within the last couple of weeks, when I have been playing a game like Binding of Isaac, I've found that the right analog stick is affecting the performance of the left. In particular, when going down on the right stick, going up on the left stick is slowed way down. There's a smaller effect when going up on the right stick and left on the left stick. I've tried resynching multiple times, and I've got a PC adapter, and it happens there as well. I went to the HTML5 gamepad tester, and sure enough, when pointing the right stick down, the most the left stick shows pointing up is about .75, rather than the 1.0 it's supposed to be.
You would think that would mean that moving the right stick down was also moving the left stick down, but that isn't the case. If I'm just using one stick at a time, there are no issues. It's only when both sticks are in use that the problem starts.
If anyone knows how one might fix this, I'd really appreciate it!