Hi, one of my 3 nest protect started having this issue a week ago. I've been running tests and trying to get it sorted but nothing seems to work. I've been reading about doing a factory rest, but it seems that it will only fix it temporarily... I've not bought these expensive "smart" devices to be factory resetting them every 3 months or so, and seeing it's a common enough issue I'm not too happy with it.
I've performed the factory reset and for now, all is well and good... But for how long?