I've rendered a few lower third animations in After Effects (23.987, ProRes 4444 with Alpha) for use in Final Cut Pro 7.
My FCP sequence settings are 23.98, ProRes 422 (HQ) 1920x1080.
This isn't anything new, I've made tons of files exactly like this before.
For some strange reason, when I lay the AE animation over the video file (ProRes 422 (HQ)) in the FCP sequence, without rendering, everything looks normal. However, after the render is completed the animations are jittery and the video it's laid over is jittery as well. The jitter goes away once the playhead passes the rendered clips. The other odd thing is that the color of the render bar for these clips is a gray color, similar to the video file as if it's already rendered (or matches the sequences settings requiring no render) and after the clips are rendered, the bar turns blue.