So I actually have had this happen before, and it did appear to be something to do with the stabs, though I never conclusively figured out the exact culprit.
In my case, I think it was the heat-shrink mod I was attempting - it was a little too wide and was causing the stabilized keys to twist a bit as they came down. I was using Durock V2s and MT3 caps and had the issue on the spacebar - took me a minute to realize it was the cap itself hitting an adjacent one.
I also have a KBD56L with KBDFans’ new polycarb stabs - and I will say that while they’re plenty smooth, they do allow a fair bit of rotation. (I don’t think they cause it by themselves, but allow for it if something else is.)
I haven’t had any caps touching on this keeb, but if I nudge them from the side they have enough free play to do so - so some amount of stab tuning may help here - though I’m not versed enough in it (or these specifically) to tell you exactly what needs to be done. Maybe try removing some of the surrounding keycaps so you can get a view of the stabs and see if you can see what/where the forces are pushing the cap this way or that.
There’s a possibility that it’s down to your typing style combined with the play the stabs have; does the key twist no matter where on the surface you press? I’d try messing around with that, too, to see if you can find any patterns there.