Seems like a bug somewhere but often when I exhibited this behaviour, it’s due to backward and forward ik/fk not being congruent solves. When you backward solve it’s most likely in FK bones to controls. From there you forward solve the controls back to the bones. When you have non congruent solves, the error accumulates. If you recompile it pops back and reinitializes. When the error is small you don’t notice it, but when you do it enough times it accumulates and you can see it.
If you goto Manny’s control rig and open it up and keep toggling the IK/FK switches back and forth enough times you’ll see it start to drift. In your case here it seems for some reason only happening on the right foot, but there does seem to be some round trip solve errors that are accumulating in the forward solve.