My suspicion would be electrical noise.
Try increasing the Debounce Interval (Config / General Config) to 2000 or so. If this resolves the problem then you need to investigate the actual cause of the noise (Debounce should be regarded as a sticky plaster rather than a cure).
Have you changed anything in the shop – added anything new (equipment, lighting, etc.), rerouted any wiring ?
Are your machine switches (estop, limit, home, etc.) and the associated wiring all sound and in good order ?
Does disconnecting your VFD resolve the problem ?
Tweakie.