Files of any size can be attached to the ticket, there isn't a limitation there.
The general way to find culprits is what you could call "bifurcation" I suppose - hide half of the scene, see if the problem continues. If yes, hide half of what was left. If no, unhide the hidden half and hide the unhidden half. And keep cutting in half until you have a manageable number of objects to check.
OFC it might not be so straightforward for a NAN, as it could be a couple of objects interacting with each other, but at least it's a (relatively) quick way to test to see.
