The animation is fine in blender but when I export it to unreal the hands are messed up i have tried multiple settings and nothing looks wrong with the weight paint
Even though this is a two year old post, I had a similar issue and I want to share what fixed this issue for me.
If your animations contain bones with non-uniform scaling in Blender, they will (sometimes) break in Unreal Engine.
First you have to make sure your animations don’t contain non-uniform scaling, but there might also be bone constraints that scale your bones. For me the issue was caused by IK constraints with the stretch setting enabled. I use Rigify to automatically create a control rig in Blender, which creates the IK constraints automatically. Rigify has a setting to disable IK stretching, but I noticed that turning off Rigify’s stretching is not enough, you have to actually disable the IK constraint’s “Stretch” checkbox.
I used this script in Blender to disable stretching from all IK constraints:
import bpy
# Replace "CharacterArmature" with your armature's name
rig = bpy.data.objects["CharacterArmature"]
for pose_bone in rig.pose.bones:
for constraint in pose_bone.constraints:
if isinstance(constraint, bpy.types.KinematicConstraint):
constraint.use_stretch = False