I have four elements, Text, Text, Image, Image all on separate layers. The two text elements are keyframed to move a bit and the first image is keyframed to move in sync with the text. The other image is keyframed independently. It's all very basic.
The mini-sequence has a green Preview render bar over it and plays as expected but when it's fully rendered the first image, the one keyframed to the text's movement VANISHES. And I'm not alone; I found a post about it here from Feb. 6th 2009:
Help!!! Let's see if I can explain this....I have taken a clip and placed it on the timeline. I applied some croping elements to it and motion...it starts our as a very thin line and then moves up and down to create a rectangle. I can view it on the timeline but the minute I render it with "full" and then view it, it no longer exists....When I export it to make a Quicktime it is gone....
What's interesting is his keyframing seems very similar to what I was doing with this image. At first I thought I goofed and had the "reveal" keyframes going in the wrong -opposite direction- but they weren't.
What didn't work was re-launching FCP, deleting render files, toggling track visibility or rebooting the Mac. What DID work was right-clicking on the image file in the timeline, selecting Remove Attributes...and ticking Crop and then hitting Okay to remove all cropping of the image.
I then re-did the keyframe cropping, rendered and it was fine.