This thread although specific to the Mavic Air is a salutary lesson on magnetic effects. Couldn’t get my Air in the air until I sussed the watch was the culprit. Leave the watch in the car now some way from landing mat or get someone else to calibrate it but it doesn’t ask me now I don’t wear it!
Definitely land NOT on a car roof or indeed any raised surface. If if doesn’t land spot on it can topple from a height and do damage to car and itself. Flat ground only. Also keep out of long grass if you can as Minis not good at mowing.
Also a possible gotcha is if using a pad make sure to hammer pegs flat to ground as if drone lands near a raised peg one of props may well get trashed. Nearly happened on my first ever go with a M2P which is a tad bigger than a Mini but noticed it was going to happen and managed to sort matters. Now use leg extensions which I keep on permanently on the M2P and use a mat.