To think this isn’t safe?

Had an excessive amount of issues with my boiler losing pressure every other day then showing an “unknown error” even when the pressure was topped up again so the boiler wouldn’t work. Repair men out near enough weekly (and in the end 2-3 times a week) to try and fix the problem. Eventually they decided it was the circuit board that was the problem and put a new one in. Boiler now doesn’t cut off when it loses pressure, it’s currently at “0” pressure but we’re getting hot water and heating fine.

Fully prepared to be told I’m ridiculous, but it’s in the red and I’m really worried it could explode or something now (though probably won’t explode with no pressure, but what if the pressure goes too high and it doesn’t cut off??).

Is this safe? Should I get them to undo whatever it is they’ve done? On one hand I’m really glad we’ve got heating and hot water again, but I’d really rather not have a faulty boiler that now overrides it’s built in safety shut off.