Step 1: Import animation
Step 2: Increase FPS (from 30->60 for example)
Result: Stuttery animation
Problem: The original animation curve tangents are maintained. This means that the animation itself is not properly smoothed out.
Current solution: go through original curves and right click (Both Tangents->Clamped Auto).
This is not the case for umotion generated curves (for example IK curves, which are clamped auto by default).
Customer support service by UserEcho