I ran in to this weird problem today. After importing a premiere project directly into after effects, I found that one of my pieces of footage had a strange glitch. My first step was to look to see if there were any key frames or expressions and there weren't any. Next I tried reopening to AE project and that did nothing. I then totally closed AE and reopened and still no luck. Finally I decided to re-import the file and Boom! the problem was fixed. I had never run into this before to today and it had me confused for quite a while. Here is a video of the glitch. hopefully this helps if you run into the same problem.
Thanks for sharing your experience—and what fixed it for you.