I see there was another thread about a bug when copy-pasting grinder traps. This bug too is happening w/ grinder so I immediately wonder if it's related. (Speaking as a software dev also -- which by the way is a job that finely hones one's troubleshooting skills, teaching you things like "be very observant; no clue is too small". ;)) I don't have many floor traps unlocked but I might try spike later to see if it does it, too.

I usually do my starting setup then copy one of those traps to have it on the clipboard. Sometimes when pasting -- and I'm not sure why -- instead of properly pasting the trap, it pastes an un-upgraded* version of the trap, and then sticks the cursor in that spot, putting it into "drag map" mode, and getting stuck in that mode. (*Note this happens even if you have the $ to create the upgraded version.)

It's super annoying in the course of actual play: 1) doesn't paste the trap you want, 2) suddenly you are dragging the map all around and the cursor is stuck in that mode, 3) you have to try to manually free the cursor by frantically clicking. Meanwhile the enemies breeze by, and you lose. It's typically cause for a restart. :(

I don't see any causation pattern. but as I write this I'm speculating if it has anything to do w/ how much $ you have when copying. I'll post more if I find out more.