We can confirm this here from Germany, have been seeing issues since about 1 AM UTC in increasing amount (although that may also be due to our traffic fluctuations). Besides the "alert internal error" we also have had connection aborts, no response after our 6 second time out and the occasional "HTTP 503 Unavailable" error. Some servers in the DNS rotation seem to be affected more than others though. Apple developer status unfortunately doesn't show anything either and the normal apple status only a resolved issue between 3:16 and 4:45 which doesn't match our logs at all.

FWIW I can confirm the same issue occurring, currently observing this for example in northern Germany for a lot of tiles around the z=12 zoom level (but I can see errors up to z=7); the tiles seem to be valid files but empty. Curiously the DuckDuckGo variant also shows missing tiles but they generally seem to differ from what we observe on our own application. The missing tiles do not seem to simply correspond to specific CDN hosts unfortunately, I get some valid tiles as well as some broken ones from sat-cdn1/2/3/4.