Can't import FBX animations

When importing Animation FBX files into 4.20 the following error is received: "Failure to Import - Mesh contains root bone as root but animation doesn't contain the root track."

The importing process works as intended in 4.19.2 (CL-4033788), this is a regression. This issue was reported and tested in 4.20 (CL-4212847). This issue was reproduced in Main 4.21 (CL-4221482)

1. Download the attached FBX files
2. Open the UE4 Editor and create a new blank project
3. Import SK_Brother.fbx
4. Import AS_Brother_GenCrank.fbx

Results: Failure to Import - Mesh contains root bone as root but animation doesn't contain the root track.

Expected: Animation FBX is imported correctly