I had the same problem with mine. Rebuilding the pedals only cured it for a short period of time before it came back. Each time I rebuilt them it happened again. Eventually I did some measuring and found the plastic that the pedals rotate in had become oval. At the time I bought a G25 to replace the well worn MOMO, which now sits in a cupboard waiting attention. I blame soft plastic and my habit of only using the edge of the pedal when braking, as I don't use left foot braking.
The plan is still to build my own pedal box, but like so much else, life gets in the way.
Unfortuneately the pedal pivots in plastic "blades" which are part of the top and bottom case moldings, but it might be possible to make collars to fit. The biggest problem here is the pedal must rotate concentrically with the potentiometer or you will have the same problem. The wear seems to be mostly in the case, not the pedal itself.
This is why I think it's easier to build my own base with the old internals from the MOMO pedals. It's also why I haven't got my finger out yet.