I found the problem. It is related to terminal dimensions and looks like a bug in Emacs, though I can't be 100% sure. The problem is that frob sets the LINES and COLUMNS env vars. This isn't strictly necessary, but solves a bug in some curses versions. However, Emacs seems to get confused when this happens. I will need to ask the Emacs devs about this.
To fix the issue for now, you can edit src/frobtadsappcurses.cc and in lines 259 and 260 find this code:
Simply delete or comment-out these two lines.