I've noticed a load of 500 errors in my web inspector when viewing maps - it's trying to load /md/v1/shield? from the CDN.
Interestingly, it only seems to happen on UK and Ireland maps. Other countries don't even seem to try accessing these resources; but if you look at a map for UK or Ireland, then you will see dozens of failed requests for these shield resources.
I don't think it's anything to do with my implementation, as I can replicate it when looking at one of Apple's example maps and repositioning to view the UK.
Does anyone know why these shield resources are only used for the UK? And why they're not working?