re-using same skeleton, always head facing wrong direction

hi, so i made a skeleton im re-using across all my characters, but im not being able to share animation properly between them. i retarget(using a custom ik retargeter) one animation from epic skeleton(animations i get from market place), onto my skeleton and works fine, but when i try to share that animation to other skeletal meshes i made that use my custom skeleton, the head usually breaks(faces crazy directions) and sometimes the shoulders and some proportions look really bad. IF i then retarget my retargetted animation to the other skelly mesh all works well, or even from epic skeleton animation to any of them also works fine. just a bit cumbersome because i pretty much need to duplicate every single animation in the game for every character.

anyone can shed some light on this on why this is happening and if theres a way to solve this? my characters are just humans with very similar proportions. i also checked the skeleton pivots across them(head and root) and they also seem to be consistent.