Nowt wrong with that, condition 1 is perfectly safe..it's pulling the trigger that makes it go bang and ultimately that was what happened here..thankfully with only the car being injured..Due to the nature of the work the Firearms can not be kept in a safe, in the rear of the vehicle or in a slip etc they have to be kept at hand in condition 1 ready to be deployed now.
First round stoppages..I assume after first shot...also caused by having 29/30 rounds in the mag, 28 is better.
MP5 is pain in the butt to chamber check....it's a double stack magazine so check which round sits proud after dropping the bolt ...it should be the opposite of when it went in.
A good post DM well detailed.