Yes power cut can damage timer.
I have had this before when isolating power to service Range Powermax boilers but have also had instances where customers have had a power cut overnight.
It's evident when the CH and HW lights are less bright than they usually are.
If your handy with electrics it is possible to wire the timer out on the wiring center to prove the rest of the boiler functions as it should do
avoid plumbcentre, they class it as a commercial boiler. their prices reflect that
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