Windows IOT v.10.0.17763.503, Raspberry Pi 3, with a WPF/C#/UWP
application.
Normally the on screen keyboard works fine, it pops up when required,
respects the InputScope setting, and goes away as expected. Every now and again, apparently randomly, the keyboard appears but all the keys are blank, they have no letters on them. If you press a key the correct letter appears in the text box, but the keyboard
will not go away. Even if you shut down the app, or kill the process through the web portal the keyboard remains on the screen until the Pi is powered off and restarted. Extensive testing has not found a consistent cause or a way to reliably replicate this.