weird hitbox issue CS:GO (again)

Hey,
I took 2 models and kept the parts I needed to create a new model. The model is supposed to work on CS:GO, so I took the original skeleton. The model and the hitbox seems fine in HLMV: http://puu.sh/8xnrW.jpg
But the hitbox bugs ingame: (screenshots are from another model I imported some months ago, but the problem is still the same)
http://image.noelshack.com/fichiers/2013/42/1382277108-2013-10-20-00004.jpg (shoot above the head, I still deal damages to the terrorist)
http://image.noelshack.com/fichiers/2013/42/1382277108-2013-10-20-00003.jpg (shoot next to the body, I still deal damages to the terrorist)
http://image.noelshack.com/fichiers/2013/42/1382277108-2013-10-20-00002.jpg (shoot in the head, I don’t do a headshot)
(when I tested, they hadn’t any kevlar or helmet)

2 years ago someone reported exactly the same problem on an official model : http://forums.steampowered.com/forums/showthread.php?t=2961742

Anyone know a way to fix this please ?

bump, the issue is coming from the model, so I’m wondering if the bug was created in 3ds max and if it’s the case, what should I explore ?