This is mostly just a heads' up in case anyone else hits the same issue I did. It took me a full week to diagnose what was going on as I was having random crashes, that would present differently when i made modifications to my kernel. For a long time I assumed my own kernel was corrupting itself, but it turned out to be a firmware issue.

Just adding a note here, in case somebody searches for the issue in future, it may serve as useful information.

https://github.com/petemoore/issue1979