Editor bug/crash

[Polygon]

In the level editor, when something is selected, I cannot move it around without cutting and pasting. I don't think this is intended, as it says I should be able to use the arrows to "Move selected region", but the arrow keys do nothing.

More seriously, when an object is selected, it says to press F to "Edit entity". When I press F, the game instantly crashes with no error message.
I think this corrupted my saves too, because it thinks I haven't beat levels that I spent hours beating.

I tried reinstalling the game, and the exact same thing happens.

Any idea why this is happening?