There is a bug in the fbx curve import code where we do not multiply the tangent by the scale parameter. Only the key value is currently scale.
In 4.25 there was a hardcoded 0.01 scale but it was wrong when we import curve for other thing then blendshape.
QA: please test both blend shape curve the attach fbx and other custom attribute curve like on a joint to be sure everything is good
In UE4 editor
Import the attach fbx and force it to import it as a skeletalmesh
make sure you import morph target
make sure you import animation
make sure you import custom attributes
RESULT: The morph target curve in the animation has tangent 100 time longer then expected
EXPECTED: The morph target curve is the same as the one you see if you import the fbx into maya
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-102564 in the post.