I think that's what we call a chainring and cog. I swapped both to no avail. I believe the issue is the crank arm spider which attaches to the chainring (front sprocket I think?) is slightly bent, not to a visible degree but enough to throw off the chainring rotation. So I'm replacing that, but they're sooo hard to find not as part of a full crankset and match to the bottom bracket.
Yeah checked my chain and it looks fine. It's probably not anything related to that, but that's one of the parts that's just getting replaced on principle now.
This finally got me to make an account. My beautiful, beloved track bike has been the bane of my existence this past week. Something is off in the drivetrain causing the chain tightness to vary wildly in like a quarter rotation. After swapping components to test for change, the only way to diagnose the issue, I'm finally just replacing basically the entire drivetrain. Not asking for advice, just saw bike thread and wanted to vent.
Building maintenance. Trust me. It's awful.