Thank you!
It was only put up in January so not lasted very long.Sounds like it's been taken off the plate at some point and put back on badly. For all my swearing at that first one this morning trying to put it back on the ceiling, the trouble's finding the correct angle to slide it in at. Putting it back "wrongly" wouldn't be hard.
I think you’re right. It was very humid and I had all the windows open overnight to try and get some cool air in before all the hot weather.@Spaniel this is just a thought, but my alarm (the twin of yours) went off twice yesterday, at 6am and then again at some point in the evening. I think it went off because of the humidity - I had some clothes drying on the clothes horse overnight to yesterday and then of course, the humidity skyrocketed again last night. Moved the clothes horse into the kitchen and it's stopped making noise AND giving red warning flashes.