When you "Deoptimize Transform Hierarchy" and scrub the animation in the Animation Window, the mesh becomes broken (detached from the joint transforms). Clicking the Editor Play (runtime) updates and corrects the mesh transforms. Switching back and forth between Optimized & Deoptimized without going into a runtime playback (Editor Play), continuously gives variations of the same issue.

repro:
-import attached project
-open HumanoidAnim scene
-open the AW
-select mangagirl in the scene
-RMB-click on the Animator component of mangagirl in the Inspector
-select "Deoptimize Transform Hierarchy" in the list of options (last option)
-scrub the AW timeline...
result: mesh disconnects from joints resulting in bad deformations.
(see attached gif)
expected result: Mesh should properly.

-click the Editor Play button, Stop...
result: mesh deforms normally, event when scrubbing in the AW

this is not a regression and happens in all versions of Unity.