It appears that view limits intended to prevent the gun from going through an optics device prevents the loader's MG from returning to the forward position. Not too sure of the best way to fix it, but at least some way to reset the gun position would be nice.
Reproduce: Enter loader seat, turn out, select "Take M240" from action menu. Gun snaps to left-facing position. Option "Leave M240" does not re-center the gun as it was found.