Hi. Thanks for the reply.
1) I checked as you noticed, but URL are the same
2) I tried all 4 combinations with no improvements.
Marker data XML directory: url1
Marker data XML URL: url2
url1 & url1
url2 & url2
url2 & url1
As mentioned: This problem only appears with iphone 5s. All other mobile devices (nexus, iphone 5, iphone 4s, etc.) work. Is there maybe in incompability with iPhone 5s?