take some pics or a youtube video.... it would really help

is the slide just not moving forward enough to allow the safety to engage?

nope, the slide is normal sir. Neway... I could not repeat the problem, so i guess I would go to the next issue. I want to know how much gas did you use to empty the mag? I can only shoot 23 bbs using hi cap 5.1 mag and shoot 20 bbs using hi cap 4.3 mag. Is this normal? What could cause high usage of gas?

Over 40 BBs in 4.3 mag
Over 50 BBs in 5.1 mag.

That is with high flow valves, too.

Any resistance in action will cause high gas consumption.