"Reimport with New Source" fails on Mac

'Reimport with new source' command does not work on Mac.

Confirmed in 4.22 @ CL 4771381

1. Create a new BP project, add Third Person Template
2. Export an Animation from Mannequin/Animations
3. Select another animation and "Reimport with New Source" (Select the fbx that you just exported)

PC/Expected: Anim is overwritten with new anim

Mac Result: No change

Output Log -> New page: Reimporting ThirdPersonRun.abc