BUG (maybe) Strange Scaling/Blanking problem

This may be a bug or it may have to do with scaling settings.

A GH4 H264 clip with a camera reposition is sped up 2000% making the camera pan a quick whip pan. All looks good.

Some color work is done on it. Suddenly the whip pan has blanking on its sides, very much like a wipe.

Double clicking on the clip with the time indicator on a 'blanking' frame places the sped up and graded clip in the Source monitor where there is no blanking and scrubbing shows no blanking. Here's the two monitors parked on the same frame:

Capture 1.JPG (261.89 KiB) Viewed 369 times

Here's the nodes with the elementary grade:

Capture 2.JPG (113.49 KiB) Viewed 369 times

The project timeline is 4096X1716. Here are the Scaling Settings that I use to get correct output on my Program monitor and on the Decklink mini 4k:

Capture.JPG (42.9 KiB) Viewed 369 times

This only appears with the sped up 'whip' pan.