As you may notice the fuses or fuse sensors of the mine are either damaged or removed. If it is a contact mine ( and it looks like that ) each damage made to these fuses ( sensors ) would cause the explosion of the mine.. however who knows that for sure....
Vickers machine gun. By the angle of the gun, the indirect fire sight and the lack of cover for the crew its being used for long range fire. The piles of empty cases, yards of empty belts and steam coming out of the condenser show its been a long fire mission.