Lately, when I export the M100 timeline edit to a QT movie with Computer 0-255 to say ProRez (from ProRez) or any codec to any codec, after a time, a note come up to say there was a memory allocation error - out of memory.
I have heaps of both RAM (4Gb) and of course HDD space. If I export as a self contained or by ref, no problem ever, just to Computer 0-255 and to any QT codec as well.
This does not happen with every export, but it does happen to quite a few.
I export 0-255 to ensure proper contrast on the DVDs that I create.
I'm in the same boat with 12.7.1. Way too many projects that are still in progress to upgrade to 13. I use virtually the same process you do in regards to exporting for dvd, but I haven't experienced the memory errors since 12.7. I'm running 10.5.5 on a 8 core mac pro. Sorry I can't offer any more insight.