For that bit in the top left, I dropped in the enclosed area with the lone guy, think I managed to get out of that by some jumping around for a bit, although I couldn't figure out how to get the guy killed. The solid vs non-solid wasn't really much of an issue with some experimentation, although I can see how players that jump on something and find themselves clipping through it might just conclude that its just how the game is set up (as a ghost supposedly works that way), and to jump/interact with something they need to possess someone.
There was a pit in the construction zone as well which seemed to block the ghost from moving northwards as well - that wasn't very apparent from the camera angle.
Oh and forgot to mention that the app comments were pretty fun to read too, good job on implementing that in the pause screen!