Well, I've had the "unusual power consumption" event now three out of the last four times after DHW production (around the time the "residual heat" feature and/or the pump would have been switched off). And now - a bit less than 24 hours after the last DHW production - the controller went offline. When I went to check, the screen on the RTB (this is one of the last 2016 models with an "integrated" screen) only flickered when I pressed buttons. I opened the controller box, and when powered on, all four lights (red/amber/green and blue) turn on briefly, then the green light remains on, and after a few seconds the red light turns on.
My best guess is that the controller performs a self test which fails. The unit is still consuming approx. 18W, but I don't think it will fire up the pillefyr when I next need DHW.
Assuming this is related to the "unusual power consumption" announcement, I'm a bit surprised that this was not picked up by NBE.
Any thoughts?