Hello,
I’ve been having problems loading aec files from C4D R11.5 as well. I realized that it sometimes worked and sometimes didn’t. I noticed that my files sizes were different too. The ones that worked were around 20k, the ones that didn’t work were usually around 200k and up. What’s the difference? I found that those with multi-pass renders and a lot more keyframes wouldn’t import.
This is how I got around it.
First, render your movies out, then go back into your project and save the aec file by itself, but turn off all your geometry and your multipass settings first. I turned off my lights too just in case. The file went from 4MB to 72K and it imported into AE just fine. Camera and nulls came through fine. Hope this helps you and others.
Brian