Updating post from Reddit.
If you google your specific boiler and 'losing pressure' or 'no pressure' you should find a solution which enables you to re-pressure the boiler yourself.
I used to rent a flat with a combi boiler and it did this to me a few times over the years. I found a youtube video from an older gent who showed all sorts of boiler resets and general DIY plumbing fixes - super niche, but really useful.
A quick search myself, have a look at this video, seems to be the same (or very similar) boiler to yours:
https://www.youtube.com/watch?v=UbBiaw8V3FI&ab_channel=jleswright
Is the plastic key back in underneath that you open to increase pressure ? I had 4 guys try to find a leak and that key was not in and none of them bothered to check...not a plumber - just my own exp. on pressure swings !
Thanks yes the key is in and in open position the plumber didnt lock it before re pressure is that what u supposed to do? I just tried by locking the key then opening it when re pressured and will see
It is open when repressuring and should be re-locked after that...my pressure was swinging all over the place before...we have similar model boiler...plus permanent drops....no longer ! Hope it works.
I think 1.5 BAR is baseline under no load, and then its set correct and swings a bit around that now - but no longer into the red zone...and never slow bleed to zero over about a month+...all that stuff gone once they key was properly locked...this boiler was in a bought flat so the key was never locked and I just found the user manual a few months ago and saw the white key was sitting out on a shelf.
Thanks so it should stay locked?? Mine has never been locked and the online guide said only to lock it when repressuring then open again?