Not the exact same frame - it seems to be around about the same time, when the computer starts sounding like a lawnmower. When I try exporting as PNG sequence there are other problems instead which stop the files from being usable.

After spending hours upon hours of drawing, compositing and everything else involved in putting my animation together, I get to the export. What happens is that quality drops severely during the export process - at a certain frame, the foreground elements become pixellated and after that the backgro...