Not sure exactly why the issue arose now, but it seems that there has been some change to either the driver or the bulbs which is affecting the control of the LZW-31SN, based upon the fact that you swapped in another LZW31-SN and the issue remained.
That being said, I’m surprised that this configuration worked as long as it did. According to the details in the Amazon listing, the mirror has a built in dimming function. That suggests that the mirror’s dimming should be controlled by the native dimming and that the LED driver shouldn’t be separately controlled by a dimmer switch.
Additionally, I’m guessing that the LED driver is an ELV driver, and the LZW31-SN is not compatible with those.
Since a dumb switch works ok, try setting the LZW31-SN’s Smart Bulb mode to On/Off only to get it to replicate a dumb switch. You won’t be able to dim from the switch, but the mirror likely wasn’t designed to be dimmed in that manner anyway.
I’m going to guess it’s compliant. The OP said that he is using recessed receptacles. So if the mirrors are mounted over the receptacles then only thing that can be plugged into them are the mirrors. So in that case so long as the mirrors do not exceed the capacity of the switch, the switch meets the NEC requirements.