The safety on a Thompson is quite positive, positively locking the bolt in either its forward or rearward position when applied. And the bolt must be in the rear for a loaded drum magazine to be inserted, which can slow down a user not familiar with it.
Watching them drive the T-34 tank around was pretty cool too.
It was much, MUCH more fun for you watching the Scaup at play than it was for the poor guy who had to drive the thing. And T54/T55s are worse.
It was on pavement. I was amazed at how quickly it moved.