I have one of the above boilers which is now just over 3 years old. It
is set to 80% of maximum temperature and the H/W cylinder stat is at 65
deg C.

It has started to intermittently trip to a fault state (red LED
flashing).

Unfortunately the installing plumber can't visit until the New Year so I
was wondering if anyone can suggest investigation steps that I should
pursue.

TIA Richard