2017 375FL Light switch

The light switch in the bath room panel is only working the lights half power(dim), it has been working fine until a couple of days ago,
The fan motor switch is working fine, there are only two wires connected on the back of the switch how does it know witch one to power up?
I tried two turn the bathroom lights on with the panel in the living room and it is dim also when they are turned on.
Possible cause??? Help!

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The panels on the newer Vanleighs switched from wired to battery powered but I believe the functionality is still the same. You should be able to press and hold the button to dim / brighten the lights.