I've replaced the 100W incandescent bulbs from the identical dimmer units in all 4 bedrooms with 18W Philips Master LEDbulb MV designed for dimming.
Everything works perfectly and as expected in my room... but in the other rooms using the dimmer control panel results in issues:
Reasonably smooth dimming for the first quarter of the turn, then the brightness stays the same for a period before jumping down in two large steps before going out completely.
When this happens, simply turning the dimmer switch back to its full position does not reactivate the light, and the switch needs to be turned off and on again.
I can confirm that the dimmers work perfectly fine with incandescent bulbs, and I've no issues with the set-up in my own room (and yes, I have switched all the bulbs round to confirm that the problem is not with the bulbs).
Would any of you electrically minded people know why one unit is fine, and the other three units all display near identical bad behaviour?