Unfortunately I cannot remember why this project got corrupted. Unlike the first time this happened to me, I knew exactly what I did in order to produce it (more information available in this SC: AUP3 corrupted project). However, for this project, I just went to open it one day and it wouldn’t.
So far, I’ve had two projects fail on me. If I compare them, both are quite large (+2 GB), but other than that, I don’t think they’re that similar. Both of them do use a lot of tracks though. The first project has around 40 tracks (stereo and mono) (this is the one that Jade helped me to restore). As for the other project, I can’t verify as I cannot open it, but I think that there are 8-mono tracks. The total run-time for both projects are very much different. First project is at 4-minutes, other one I estimate at around 35-40 minutes. I do use Copy/Cut/Paste a lot.
I do use the Envelope Tool and I know for a fact that the first project that got corrupted (that Jade helped me to restore) uses it, as for this project- I am not sure.