Thanks Dave!
Strangely enough, I adjusted the secret settings to purge after 50 frames and I’m fine now, or so it seems.
I have no idea why, if this was the solution, Quicktime would have any bearing on the success of my renders, but I un/reinstalled so many times I can’t believe it was a coincidence.
Is there something deep in QT that is hogging memory AE is trying to use?
Computers… hate figuring them out, yet chained to them for life 🙂