Fix interpolation of constant on Unity 2018.4.0f1. Rotation curves are tested.
You can select *.anim file or select animation clips of FBX.
1.Select animtion in Project window
2.Click menu: AnimationTool->ProcessForConstant
3.Done.
Animation in Maya
FBX imported into Unity. FBX settings are default. But this curve is wrong.
Animation result after processed.
Notice:
1.Keyframes must be full in animation. Please try bake keys on every frame.