I have two issues, both connected to keyboard use.
The first is more common, and is wildly reproducible for me: Whenever I go to use any of the 5 (no, wait, 4 now *ahem*) potions or capsules, the next time I try to chat anything, my text input will fill up with a constant stream of the last number I pressed. Obviously, I am not still holding down the number key while trying to type. The only solution I've come up with to clear this is to hit Escape, change from fullscreen and then back again. For whatever reason, that seems to clear whatever's buffering the thought of me holding the number key down. Note that I don't keep using the item in the associated quickslot, it only shows up in the text input.
The second seems to happen more when changing between navigating with the mouse and keyboard, but is not as frequent. Sometimes my knight will be stuck moving in a direction I am no longer telling it to go, again as if I was holding down a key (in this case a direction key). I've found the same "fix" works, with switching back and forth between fullscreen and windowed mode. This isn't a great solution, though, as my stubbornly walking knight may be in the middle of a battle at the time.
I play on either my laptop or desktop, both Macs, and these issues occur no matter which computer I'm using.
I have the same problems on both my PC desktop and mac laptop - thanks for the resolution fix though. It'll work better than exiting the app and logging back in.