1. The skill projection shadow doesn't work properly for permanent skills or blockers
2. If a projection shadow hotkey is released while the game is paused, the projection shadow remains visible until either the game is unpaused, the lemming is unselected, or the other type of projection shadow is activated
3. The projection shadow appears behind objects, if those objects are not set to No Overwrite
I've decided - this isn't worth holding up V12.8 for. I'm going to remove this feature for now (obviously, I won't delete the underlying code, rather I'll just disable the feature), and look at it again for V12.9.
As of commit 9f2b4b9 (where I've now merged this into the master branch), I'm pretty confident the projection shadow feature is good to go. A couple of minor bugs remain (most notably that it doesn't disappear when paused until the mouse is moved), but nothing critical.