I animated my weapon in Blender, but when I exported the model and imported it to Unity my model flipped and is acting very weirdly. I tried changing the export settings, but nothing fixed the problem.
I used IK and Child of modifiers.
Blender Axis is Zup and Unity is Yup (Yup Maya and many other 3D apps)
Exporting FBX From Blender To Unity3D With Correct Rotation
Everything that @sadicus says above ^ ^ ^ applies.
Here are my data blurbs on Blender3D and Unity3D:
Blender3D import FBX:
https://discussions.unity.com/t/832303/2
The script that Unity uses:
./Hub/Editor/2020.2.1f1/Unity.app/Contents/Tools/Unity-BlenderToFBX.py
More on fixing it:
https://discussions.unity.com/t/839045/4
Blender3D objects used as trees / detail in Unity3D terrain (See the second half of this response)