Ha, are you kidding? Safari 5.1.7? That is the last version before Apple retired Safari on Windows five years ago, right? Nobody uses that any more and it's not useful for testing - I'd avoid using it at all!
I did test on iOS 10.2.1 and it worked fine. I think you'd best follow the guidelines for a bug report to investigate this further, i.e. create a minimal .capx that reproduces.