Sometimes, keyboard input from my Windows 10 phone suddenly stops working. Apparently, the keyboard events are buffered somewhere and are not reaching the session until "something" happens. Right now, "something" seems to be closing the keyboard with the toolbar button. This is with version 4.6.0 against eudemo.thinlinc.com, and also with 4.7.0rc2 against my workstation.
The prioritization is low mainly because we believe that the market share for Windows 10 mobile is low.
Windows Phone is discontinued by Microsoft. We will not be fixing this.