I reproduce a bug where dragging the keyframe position affects its value. You appear to experience some sort of corruption resulting in unexpected interpretation of the value by the filter image processing routine, which I have not yet reproduced. I have not yet figured out the source of the bug I found. I will keep looking, and maybe it will be related to your problem.
Maybe I was completely false with this!
If you use that filter without any “background”, is meaning another video part under that video part, the effect looks “wrong”!
I have as “background” a simply black part, but this part was not as long as the part with that filter (you know what I mean?).
But I still have a further look on it…
I understand. I too used a color clip on V1, but I had it stretched the duration of V2. It is important to remember that all upper video tracks blend with V1 instead of a hidden black background.
Ok, I just have a little trouble with the replay in editor, so I cannot go further with testing, because of that bug, or “bug”
I had copied a video part with fade in, witch runs smooth, and the copied part is “frame-stutter-stutter-stutter-frame”, wtf?!
But ok…
------------- EDIT 1 --------------
DIRECTLY EDIT!
Restart of SC, all fine, is meaning, it’s now the same way, smooth.
------------- EDIT 2 --------------
DIRECTLY EDIT 2!
First playback, smooth (ok, more or less, but smooth), second…: Stutter Stutter Stutter. Again restart of SC, first time smooth, second time stutter stutter stutter… wtf!