sotrue thanks for that, I can see the crash on my end as well (with a lot of memory use). This is caused by the export process quite primitively loading the entire file into memory for processing, which just runs out of memory in your case.
The good news is that this is something that's already mostly fixed for next update (released probably towards the end of July), where exporting will stream from disk instead, and only require a fragment of memory it's using now.
However, there is a gotcha... the update probably won't cover m4a yet (only wav, mp3, ogg/opus, and some instances of aac are done as of now, and even those are still somewhat wonky as I'm writing this).
If this ends up being the case, one way forward will be converting to one of these formats first, and then re-opening the converted files. The audio file node will pop a dialog that lets you keep the timeline clips, so you'll be able to swap the audio file asset out easily once converted.
I know that's relatively cumbersome even with the upcoming fixes, and this is probably not the answer you were hoping for, but it's a known issue that'll be fixed over time... can't really tell when for m4a yet, but the rest of the formats you use in your project will have the problem fixed