If you place any mines near objectives, they don't let you interact with it. I can confirm it also happens with cogitators, so I'm assuming it has the same effect on any interactable object.

Here's how to replicate:

Start a silence the guns mission. Go to objective, lay mines near the guns. Try to interact with objective.

Workaround:

Do not lay mines near the objective, if you did, find a enemy and lure him to the mines.