[BUG][EDITOR] Terrain Piece Keeps Rotating On Its Own

[Nessy]

Steps to reproduce on NL Editor 1.15:

1) Place a terrain piece onto the level. It can be any piece from any graphic set.
2) Now delete that terrain piece and click the "Rotate" button to the left of the editor window (not the keyboard shortcut).
3) Now place another random terrain piece (doesn't have to be the same one). The terrain piece will now continuously rotate until you click the "Rotate" button again (not even using the keyboard shortcut works).