To reproduce (or just look at the video):
1) Create new project and import the attached package
2) Select either FBX in Animation folder
3) Drag "Female_Terraf...." model into the animation preview to change from skinny tall guy to an uncolored female body - it doesn't reproduce on that skinny guy (suspicion: generic (non-humanoid) bones used on female model)

Actual: Drag manually through the clip and notice that the bones are garbling up at some moments of animation

4) Expand the FBX and select the animation clip itself

Expected: Drag manually through the clip - now everything is okay

Not reproduced in 2018.1.0a4
Reproduced in 2018.1.0a5, 2018.1.0b1