Peter K wrote:
The 3 have the problem as follows:
Light Brightness works fine, until you switch the fan on.
once you switch the fan on, it operates at the speed you selected,
but then the receiver stops responding [the piezo buzzer in the receiver
does not even beep to indicate that
it received a valid button press.] , and just holds the same state
(Brightness and Fan Speed).

I wonder whether the fan is generating enough noise to crash the
microcontroller? Perhaps a suppressor has gone, or the power supply drops
out enough to crash it when the fan's running? I'd look at the supply rails
on a scope to see what happens.

Just a thought...

Theo