The hassle is could you turn around once you crawled through that mess! I think a camera might be the best solution to try to see what's up. Once you've identified where it is, then you could cut into the ceiling or decide if you could fix it another way. Another thing, once you crawled up there, would have have the tools you needed to fix it? It would be a pain to have to do it multiple times! An IR thermometer might help isolate the area, but it would be iffy. If you had one, or could borrow one, it might lead you to the right area.