Stiff tone pot, hard to turn even with contact cleaner

So I'm building a partscaster, and a tone pot on my old strat had gotten hard to turn but I just left it like that. Now I'm transferring that pickguard and pickups to the new strat, and knowing it'd be hard to turn, I bought contact cleaner to spray into it. I sprayed some into the vol and 1st tone, and now they are super smooth. For this one I spray CC into it, it becomes SUPER smooth, but once I put it back on the pickguard and tighten the nut on the top, it becomes hard again. I thought for sure maybe some dirt inside just hardened again, but I repeated this twice more, and the pot become very smooth.

So I left it for 20 minutes each time just to confirm that it turned smoothly after a while and it wasn't just because fresh CC was on it, but each time I tighten the nut around the top below where you would put the plastic knob, it becomes hard again, and stays like that even after I loosen the nut and take another look underneath the pickguard. This makes absolutely no sense to me. Functionally, the tone pot works as I've been testing it with a screwdriver while plugged into an amp with no strings on. This is driving me crazy, any ideas what the problem is?