After breaking the car at the track day I let it sit for awhile.
Eventually though, some Mini club friends put together a tech day and I sucked it up and bought the part to fix it. The issue was the belt tensioner, and after we got it off we could tell the damper on it had completely blown out and failed. I bought a mid-range 3rd party OEM style replacement. I didn’t go to the bottom of the barrel and get the $70 one, but I didn’t pay the BMW premium of $300 either.
Replacing it was ok-ish. It took 2 of us about 90 minutes to complete, with at least 30 of that trying to get a single bolt out (an offset wrench would have saved a ton of time, but we didn’t have one). It also could have been done with one person, but 2 made it a lot easier than constantly switching from top to bottom to get the old one out and the new one in.