Blue Fan Switches wrongly reporting non-neutral

A few days ago I noticed that one of our fans wouldn’t switch into high speed. Remembering there is some issue with non-neutral installations and max speed, I checked the power source attribute and it’s reporting non-neutral.

Now I find that every Blue fan switch in my house whose switch mode is set to Ceiling Fan is reporting non-neutral. This isn’t an old house; every switch box has a neutral and this isn’t an isolated case of the neutral wire being loose or disconnected. Strangely, the switches set to Exhaust Fan mode are fine.

Air gapping the switches returns it to correctly reporting neutral and allowing the fans to go into high speed mode.

WTH is going on here? I’m on the latest firmware and drivers (Hubitat).