one time, when i was a kid, my grandma gave me a lift to her place, and when we got there, the whole house was full of smoke. after running round trying to find the source, we found a small potted plant upstairs in the guest bedroom which was burned, and the plastic pot was completely melted basically to a liquid. there were no electronics switched on in the room, there was no mirror or glass object that could have focused sunlight to cause this, and it was a cloudy day

in 1994 me and friends went to set up a pirate radio transmitter on site of former NHS mental hospital which had bad reputation and was considered cursed (mostly abandoned with a few former patients squatting it). We found a working 230V socket, but the TX didn't work, our CB radio didn't work either and nor did our mobile phone - entire radio spectrum from 27-900 MHz wiped out by /something/ unknown. Been working with RF 30+ years, never encountered anything similar since.