Anyone ever find occasionally on coming back to your car the source has changed from dab to fm? I get this now and then but can't quite work out a pattern.

Yes i get that but the change is from DAB to AM, very annoying, as you say no pattern to it.

Mine generally is fm but did get am yesterday

Is it the same station on FM or just a random one?  There is a setting to automatically to change to FM with a weak DAB signal, I had to turn it off in the Mk3 as it just kept changing every few minutes.  It was called DAB Servicelink on that but might be different on Sync3.

I find that DAB loses signal for a minute or so when I get in the car, despite working perfectly when I parked the night before.  

When listening to R2 my Fiesta often changes from DAB to FM and back in areas of (I assume) poor reception. Don't notice it has happened unless I happen to be looking at the screen - one of the few things on Sync 3 that seems to operate seamlessly so far!

I think mine generally is the same station but yesterday for the first time it was on AM 1152 or something.

I've seen this on mine twice and on each occasion it seemed to be related to removing a music usb.

No, I don't understand either.

Definitely not usb with me as never use that. I'm more happy I'm not alone though lol

Another thing I forgot about as it happens less often. I can come back to car to find the temperature for heating has changed since I left it.
Car is haunted I think.