our microwave would turn itself on in the middle of the night. The famous "intermittent" problem.
I called a guy out on it 13 months after I bought it. He knew it was intermittent, and was scratching his head on how he was going to investigate. He leaned on the top of the microwave (buttons on front) and it went off all by itself, it started cooking. He was really startled, but convinced.

Even though it was past warranty he gave me a script to buy a new one and took the old one out of the house.

I'm glad you fixed your smoke detectors. all those beeps would drive me crazy.
and i'm also glad you didn't suffer a more serious loss this time.