Couple things can cause that. First go through your animbp asset override editor and see if you have a blendspace and/or aimoffset. Some just have the aimoffset, some have both. Make sure you re-target those. Once those are re-targeted, open up the re-targeted aimoffset and/or blendspace and you need to make sure the “Preview Base Pose” in the additive settings is using your idle anim (if it uses an additive. Some do, some don’t), not the original -
Next, you need to open each one of the aim offset anims IE: Aim-Up, Aim-Center, Aim-Left, etc and set the additive there to your idle anim (These always have an additive)-
You can find all the aimoffset and blendspace anims here -
If you do all that and it STILL acts like an Ostrich, open the mesh back up in your model program, detach the root from the rest of the skeleton and set the rotate transform of the root bone to 90 on the x axis then re-attach the root. -
Check the “Blink” Anim too. It uses an additive also as do some of the attacks.
EDIT: Now that I think about it, if you are importing it to an existing skeleton you shoudn’t need to re-target everything, only the animations you want to change. Do the last step of rotating the root bone and that should be it