All AadjPpneMwlkSrasWrflDup_* anims (adjust prone up, rifle, moving), except for AadjPpneMwlkSrasWrflDup_f (front), have broken interpolations. As a result, when you are in "adjust prone up" state and move to the back, left, right, etc. the player switches to the default prone animation (AmovPpneMstpSrasWrflDnon). All pistol variants, on the other hand, work ok.

To fix this, remove all InterpolateTo values for all those animations (since they are inherited from AadjPpneMwlkSrasWrflDup_f, which works correctly)

E.g: Change this:

class AadjPpneMwlkSrasWrflDup_r: AadjPpneMwlkSrasWrflDup_f
{
	file="a3\anims_f\data\anim\sdr\adj\pne\wlk\ras\rfl\aadjppnemwlksraswrfldup_right.rtm";
	speed=0.91666299;
	InterpolateTo[]=
	{
		"AmovPpneMstpSrasWrflDnon_turnL",
		0.02,
		"AmovPpneMstpSrasWrflDnon_turnR",
		0.02
	};
};

To:

class AadjPpneMwlkSrasWrflDup_r: AadjPpneMwlkSrasWrflDup_f
{
	file="a3\anims_f\data\anim\sdr\adj\pne\wlk\ras\rfl\aadjppnemwlksraswrfldup_right.rtm";
	speed=0.91666299;
};

I've tested it myself and it works.

I was gonna make a mod for it, but it would be better if you fixed it yourself.