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:
Here's the nodes with the elementary grade:
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:
This only appears with the sped up 'whip' pan.
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:
Here's the nodes with the elementary grade:
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:
This only appears with the sped up 'whip' pan.