How long, approximately, does it play for? There seem to be a few people on the forums reporting similar things at the moment.
If you run: lsb_release -sc in a terminal on your Pi, what does it say?
Possibly related:
http://forums.pimoroni.com/t/pirate-radio-vlcd-stop-after-1-2-min/5807
Edit. I think it’s another case of:
http://forums.pimoroni.com/t/pirate-radio-after-update-from-jessie-to-stretch-instable/5698