I also have your first problem occasionally.

What's happening is the one window sees one of the mouse-button-down events, the mouse then jumps (why?) to another window, and the original one never sees the mouse-button-up event and seems to get stuck in look-around mode.

Every time I then try to move the mouse to that window it jumps away to another one.

The solution I use is to use the PiP hotkey to make the stuck window my main one, then just press & release both mouse buttons. It then goes back to normal. I've not figured out what triggers this though.

Your second problem sounds like something else I've seen, where the toon sees the 'move forward' key down-press event, but misses the key-up event, and keeps moving. I usually get this when I'm holding down a movement key while I move the mouse out of the window into another one.