Having a bug to compensate for this threat existence. I promise it's a nice one.
The issue is related to the green balls and when one uses them for shooting around the corner:
Sometimes, and I don't know exactly what's going on, it happens that if you left-click at one of them - the character steps properly to the neighboring tile and if you shoot - then sometimes instead stepping back to the original tile, he stays at the one from which he shot. The game then thinks he is back on the original tile but visually isn't. So any further movement is calculated from the original tile. But if he shoots the next turn while he didn't moved yet, the game will think I'm shooting from that step-aside tile on which the game thinks he isn't but visually is. So you don't have a choice anymore. I hope it makes a sense:)
I don't know what triggers it yet. I have seen the character shoot and step back properly and next turn when repeating the exact same course of actions the bug occured. So it doesn't seem related to the cover place itself.
Probably will add a flat plane with arrow.
A flat plane with arrow is good idea. Though perhaps make it the same color /elevation / material as the shotgun cone, so it's obvious to what it relates.