Tested on Windows 10 Mobile, but as far as I know a problem which appears on all devices:
1. Bring up the keyboard by pressing the keyboard button.
2. Close the keyboard from the keyboard itself, ie press the device back button
Now, the keyboard button is still highlighted, and the code still believes that the keyboard is active/visible. If you press the button again, the button will be longer be highlighted, but nothing else happens, because the keyboard was already hidden.
As far as we know, fixing this is difficult since it is not possible to determine if the keyboard is visible or not. Instead, my suggestion is to change the button from "toggle keyboard" to "activate keyboard". The code would need to re-set focus to the input field so that the keyboard is visible for sure.
(In reply to comment #0)
> Tested on Windows 10 Mobile, but as far as I know a problem which appears on
> all devices:
None of the browsers on iOS have this problem. This is a problem on Android and Windows mobile.
*** This bug has been marked as a duplicate of bug 5547 ***