What I have reproduce (copy past of the 8298 ticket AT soldiers animations: Odd Behaviour)
FORUM THREAD all videos on 1 page :
Standup with nlaw+key shift & W+key X=change to primary (appear sometime)
Some time you just have to go crouch or stand up with nlaw to change weapon alone (end of the video)
Standup with Sec_weapon change to nlaw and press key X=change to primary (appear all-ways)
Prone and Take an Nlaw in inventory=standup (appear all-ways)
Fire nlaw and key Z=change to primary (fixed on the ground)
Standup with nlaw and just press key V=Little animation bug
Standup with nlaw and just press key B and key X=Little animation bug and change to primary
Standup with nlaw and just press key Z=change to primary
Prone and take Binocular+key X+key X+key X=change to primary and binocular for heach positions
key shift & W -> fast forward
key W -> forward
key x -> standup to crouch and crouch to standup
key Z -> to prone
key B -> Binocular
I notice that sometime when you take an nlaw in the inventory it appear on your character with a nlaw missile and sometime without.