When I stop sprinting my character will automatically go prone when I don't even press "Z". It happens at least half the time when I have a primary weapon and every once in a while with a hand gun.
- Legacy ID
Starting from still positition standing upright.
Start sprinting holding the shift key (default key bindings)
Stop sprint by letting off the shift key at any time.
end result in the character automatically going prone.
This bug will occur at least 50% of the time when using a primary weapon. Not so often when using the secondary weapon (pistol)