I’ve been having a very similar issue. The only difference on my setup is that the Red Dimmer (three way with dumb switch and relay disabled) will “crash” when the load that is traditionally controlled by the switch reaches a low setting.
I first noticed this when I would turn off the load from another switch; when the light fixture reached roughly 20% brightness, the switch would spontaneously lose power. When this first began happening the Red Dimmer switch would immediately power back on. However, as time went on, the switch would remain powered off and could sometimes be brought back with a power cycle of the air gap.
Worst yet, the switch has since become completely unresponsive and refuses to regain power.
Does anybody have any suggestions? My wife is losing hope in our Inovelli switches! Help!