Sequencer Curves View: Fourier Transform Curve Filter stopped working?

The Fourier Transform Curve Filter seems to have broke in 5.3+

[Image Removed]

• UE5/Relase-5.3
• Sandbox/Anim/ControlRigExample
• Add the Mannequin rig to your viewport
• Create a Level Sequence if you don't already have one
• Drag the Mannequin into the level sequence if needed
• Right click on the section to the right of the control rig  'Import Anim Sequence into this Section'
• Select one of the controls on the rig and open up the Curve Editor
• Open up the Curve Filters.   Last icon up top of curve editor to the right.
• Select some keys and try to use the Fourier Transform filter.

Expected Result:  The selected keyframes should be 'smoothed'  removing spikes/jitter..

Actual Result: We seem to always get an interpolated flat line between the keys instead of smoothed result..   see animated .gif  in Description