This concerns the Bis_fnc_ambientAnim "GUARD" and "LISTEN_BRIEF" settings. (not ambientAnimCombat)

When applied to a human player in multiplayer (e.g in a cutscene), the character goes on a loop between GUARD and getting the weapon off his back endlessly.

When the "LISTEN_BRIEF" animation is set to play, the human player does the animation stance but immediately reverts to the aiming main weapon stance, even if there is no weapon.

These animations on an AI (playableUnit but NOT occupied by human),right next to the human, play flawlessly!!

Replacing the "GUARD" and "LISTEN_BRIEF" with any of the "STAND" settings works fine on human players.