Animation Montage Details Panel Closes When Attempting to Update Animation Segment Data

Occurs 5/5 times. 

Details panel in Animation Montage goes blank when fields (Start Time, End Time, Play Rate, Loop count) are clicked in to update data.

This defect also occurs when clicking in the timeline in the Animation Montage details panel. 

Regression does occur: Animation Montage data in Details Panel is updatable in //UE4/Release-4.27.2 EGL Live @ CL18319896.

Repro Steps:

1. Open TPS blank project.
2. Right click in the Content Browser and select Animation Montage from the Animation Menu items.
3. Select the SK_Mannequin_Skeleton.
4. Select an animation sequence from the Asset Browser and add it to the 'Default Track' in the Montage Animation Editor.
5. Click the track to select the animation sequence.
6. In the details panel, try to adjust the 'Start Time' or 'End Time'

Expected: Data in 'Start Time,' 'End Time' is updated.
Actual: Details panel appears to close and goes blank.