Thanks for the info and help.
I thought about blurring the pictures, however, they are being animated via the camera’s depth of field.
After a few failed renders, I realized that the first successful render was done at a smaller comp size than 720*486. So I rendered the new file at 648*486, like last time, and had no problems. Not the ideal way to do things, but luckily, when imported into Avid, the difference is very minimal.
But I will look into pre-rendering and using low-rez proxies.