my god i just figured out what is wrong... i think i just did it... i remember that when i moved the bones for my mesh... i just like... moved them in the axis but did not ROTATE THEM... that is what is goin on, the arm is following the path properly, only that the bone is perfectly straight, so its not following a curved shape... its just going in a straight line that changes its height at some points... DAMN, IF THIS IS THE ANSWER... I HAVE A LOT OF WORK TO DOOOOOO

weights are not actually all automatic, i did that the first time but then i changed it. When i preview this in blender with the normal skeleton it works but when i import the pose from rochelle, it does... that... The character im rigging has the arms in T pose and ro's in A pose so... its bringing back the bones to an A pose which leads things like that to happen lol.

https://steamuserimages-a.akamaihd.net/ugc/788626099521520254/D3F2B8686F91D33C4D6838CF852F890AF9D85E2A/

i tried to crop off everything that could get banned or something (whatever idk) by valve and show just the only important bit... the... can we still call that an arm?

i'd rather not pass those images through here as this is a mod for a friend and... it is a bit of a uhm... nude mod :P
He knows i have over 1K hours in blender so he thought that meant i was an animating master god like being but seems like i am not lol. If u want to see the images i'd rather pass them to a private chat or something just in case steam has something against that. Also, the model is not mine, he personally requested one he found on the internet so its a bit weird working with a geometry i havent made myself and that i have seen for the first time like... yesterday at around... 10 pm i guess? And it is also my first time making a mod for l4d2 that modifies characters... i guess that trying to look good on my first try and trying not to disappoint my wanker friend is way too much to ask of me lol XD (also, this mesh has a technique that i felt was quite interesting and have never seen in my life to make eyes look at the player at all times without actually moving, its like the eyes rather than being actual balls, they are like... a weird cavity with a sphere inside and that makes a weird effect and stuff... which is why i decided to give it a go for the first time, as it meant less texture/animation work for me but... guess i was wrong...)

oh wow ok i did something... i just imported the producer.smd file in the animations folder which changed the skeleton and wow... just woow... this is so damn creepy... the arms are the only thing freaking out here so... time to get to work i guess lol

its the world model, so i guess that to find where the problem is i'd first need to be able to test the animations beforehand in blender, how can i preview an animation from l4d2 in blender? like what is it that i need to do? or if it is even posible to do so... XD

so i went to the street for a while to buy some stuff and now that im back i have been making some tests changing the weight paint and while posing in blender, it seems alright but in game it somehow manages to fuck up lmao, any advice about how i could fix this?? i guess im not posing exactly the same as in l4d2's animation (obviously XD) but still, the rest of the body looks fine and is rigged properly... im thinking about leaving it that way as a sort of a signature of my work lol

well, i just tested it out and seems i just managed to kinda fix one of the arms... and make the fingers look like greedo's lol

yeah, i have a lot of experience in blender but i had never before tried animating something so complex like a human being with FINGERS!!! so far i have been modelling objects like weapons, buildings, parts etc, which i have been doing for a long time so i got that covered... The problem is not modelling, the problem comes when i try to rig the thing... since i have never done it by hand, and i have always relied on auto rigging tools like mixamo's tool and stuff but yeah, i think i'll have this ready before this night, hopefully with good results, thanks!