I should also mention if I solo through an area that is suspect, and ask partner to rejoin, if I am still in the problem area it is an instant crash. Often there are areas such as fighting the roots in act II where it was literally crashing every time we started, including on save.
I backtracked to the creche and am facing the same problem again, everything ran fine until we reached the cutscene where the gnome gets shot, and now suddenly its instant crash on split screen again.
