At around 37:54, a guard is shot down by Gi-hun and rolls down the stairs, but is alive again in the next scene when #390 is shooting at the guards.
When Young-Il runs out of ammo, he cocks his weapon to reload. When an MP5 runs out of ammo, the chamber remains open and all that is needed to reload is to switch magazines and release the chamber forward. No need to cock it again.
After the restroom fight scene the prize total increases but the serial numbers are the same on the banknotes DL0338550E.
At around 22:40, as guard is dying from player 120, above player 246, you can see crew standing with camera.