I've not used my Mister in a while but came back today and seem to have an issue with my keyboard.
I initially was playing with the Sinclair QL core and the keyboard was fine but when I went to mount a Microdrive the keyboard became unresponsive.
I then tried the Commodore 64 and 128 and had similar issues. As soon as I mounted a D64 image the keyboard goes strange. When pressing a key the cursor on the 64 turns black. The number keys change the cursor to different colours and the Q key seems to move the cursor down.
As I said.. all these issues seem to happen after I use the mount option in the cores.
EDIT: It seems to be something to do with when I use CRTL+F12 to bring up the settings.
If I used the OSD button instead it's fine.