I've found this on two MG placements (static placements on the map, non-player built).

The MG nest East of Morton, pointing on the coastal road - If you attempt to mount the mg your character goes prone and does not interact with the gun. (around 058043

I also found the same issue with the placement on the NE corner of Tyrone which I believe is roughly around 049090.

Testing while being FIA, which is useful way to ambush players for gear.

Thank you