I’ve noticed this behaviour in the Safari browser in iOS 9.1 on an iPhone 6:
- User clicks on login and fills out modal login box.
- After submitting log in credentials - Safari attempts to log in but modal sticks on screen and browser hangs indefinitely.
- Only manually refreshing the page lets user proceed.
- User is looged in when browser is refreshed.
This has been tested on several different Discourse installations - occurs with each.
Other mobile browsers such as Chrome do not have the issue and work as normal. Desktop Safari is not effected also.