Well mine was off this morning (at 4:45am when I got up for the usual trip to the loo!) 3c outside and 13c inside! New boiler had gone off again, did the same during the last cold snap. Luckily I know what it is, the water pressure drops!. Problem was finding instructions on how to top it back up!. 99% of Baxi’s information sheets/videos show the usual mechanical circular pressure gauge with a needle that moves, mine only has a digital display with error codes written in ancient Greek or something similar!. I eventually found a video that was close enough and managed with that, pressure now at 1.6 bar and boiler back on.
A drop in pressure indicates a leak somewhere 99% of the time. Less so is a build up of air in the rads, so worth bleading them. Also worth looking outside at the blow off valve pipe, see if you can see any drips or wet patches.
The newer baxi’s especially the 200 – 600’s don’t have the old style pressure guage which is a bit of a PITA.
If it does it again get them back in to check, as you don’t won’t your cockles frozen early hours, especially a the weather is turning colder.