Problem with keyframe effect - at start and end (crop and scale)

Question

I'm having this odd problem with keyframe effects.
Setup:
I have a gif image that I have on video 1 for say 2 minutes.
I have my real video on video 2.  It is a person talking.
First I start with my video full size on top of video 1.
Though the motion and cropping keyframe management I slowly reduce the scale and crop my video image so that it is reduced to the lower left bottom of the screen, on top of the gif, which is now revealed.
My problem is at the start and end of the transition from full video to small box on lower left on top of my gif I often get 1-2 frames where the video goes blank and/or I get a bunch of random red bars on black background appearing on the video - Or I get the gif from video 1 without the video 2 at all (it disappears).
I've tried moving my start of end of the transition to skip the bad spots - but these new transition starts or ends not get their own bad spots in the same way.  Its only a couple of frames but it's really unacceptable for the finished video.
Note, when I say transition here I don't mean real transition events, but rather the start of effects that are managed with keyframes.  My move from start to end of the effect runs for about 4-6 seconds.
Any ideas?

Answer 1

Bill,
Here is more detail and screen captures.
Concept:
I have 3 minutes of video.  It contains a person making a speech.  During parts of the speech I want to reveal a graphic image that will be discussed.  The speech will begin with the speaker full screen.  Half way in, the speaker will shrink down to 45% in the lower left corner of the screen.  While the animation occurs (the shrink, move and cropping) it will reveal the graphic below.  The graphic will take up the full screen with the speaker at 45%.
Technique:
I put the video in Video 2 and the graphic, a GIF image in Video 1.  The scene begins with the speaker talking at full screen.  After a minute, I animate the move of the speaker using Motion: Scale and Position and Effect: Crop changing Top, Bottom, Left and Right sides.  The animation occurs over approximately 8 seconds.
I am manually adding keyframes at the start and end of the animation.  I set the ending state of the video image in the end keyframes.  The interpolation between these start and end keyframes should be managing the animation.
Problem:
At the beginning and end of the animation – usually 1-3 frames from the start and 1-3 frames from the end, where the change has barely begun or almost ended, I get these problems.  On some frames, the video (in Video 2) completely disappears only showing the Video 1 GIF image below.  On other frames, the video image turns black with horizontal red bands half way across.
Troublshooting:
I’ve tried deleting all start and end keyframes and moving the start and end earlier or later to see if I can fix this, but the problem continues to show up in these new locations.
I have added a few screen shots.
1:32:15 is the start of the animation change and 1:40:22 is the end of increasing from the mini video speaker to full size (on top of the GIF).
At 1:40:16 the video image completely disappears only showing the GIF below.
At 1:40:17 its back and slowly increases in size through the interpolation until it is full size at 1:40:22.
Let me know if you need anything else.
Thanks!
Evan