This is a bug that seems to always occur when switching from pistol to rifle when prone.
What happens is the following:When switching from pistol to rifle for the first time when prone, it causes the character to stand up momentarily and then go prone, then completing the switch to rifle.
This is very disruptive of gameplay, locking you in place and giving your position away.
1.Go to editor
2.Create Unit (OPFOR. Doesn't matter the specifics)
3.Go prone
4.Switch to pistol (Should be alright).
5.Switch back to rifle.
6.Observe bug/glitch happening.
Confirmed. Also happens when switching from the rifle to the handgun when prone.
Often when going from handgun to rifle, the character will exessively change postures several times, then just stay standing waiting for a bullet between the eyes before deciding to lay down again. Hugely annoying.