I have a (now inactive) model which as it became more complex inevitably became unusable. It was a collection of parts, subassemblies and major assemblies with screws, nuts, washers and other parts - the primary reason for such detail was to develop a comprehensive parts list, which it finally did quite well.
At first these were only assemblies of bodies, but as the assembly grew, it became necessary to make each part a subcomponent (in a file) and referenced to its own ground before being installed in the next higher assembly and joints made to hold the parts together in their designated locations.
By the time I reached the final assembly, it became extremely difficult to keep all the parts together - they would import in strange locations and be unmovable because they were assembled at the next lower level and installed using a joint to hold it in the final assembly. Crashes were not uncommon - and usually marked the end of that version of the model. I could break the links, but that would also mess up generating my parts list.
Eventually I got the model to hold together after rebuilding it several times, but the cloud renderer couldn't keep things together and parts would fly off into unexpected locations (see attached rendering)
It would successfully render using the local renderer, but even running flat-out my computer took an hour to render this model.
So there's something funny in the joint algorithm. Things are getting lost when you get enough levels deep. The smallest parts would be what would fly off, so at maybe 3-4 levels of abstraction it would lose track.
Hopefully this helps. Fusion is a wonderful tool, but it has some annoying limitations that get frustrating.
