I finally found it. No fix though.
It's due to honor mode ruleset.
I tried to start several games with basic ranger Tav.
Tactician or Custom with Classic Ruleset : No problem whatsoever.
Honor Mode or Custom with Honor Mode Ruleset : Missing audio, no sound when hitting the ground with the bow for exemple.
Still super weird. And it's quite hard to bring yourself to play without honor rules after a few playthrought.
