I ran into this problem a few weeks ago. I even went through a trouble ticket with Gaia Clary, of AvaStar fame 🙂 trying to find what I was doing wrong. Today I filed a JIRA Bug Report: BUG-7185 – Animation Import Failing in ADITI.
I finally imported the problem animation to the main grid and found out it works as intended there. The problem was only on ADITI. The video shows the problem in action.