While waiting for a part to rebuild, I thought I would throw out this 'heads up' I rolled back before a 'split feature' on a multibody part to add some features into the tree. When I was done, I rolled forward, and the whole tree erupted in blood.
I got concerned for about a second, especially after I supressed the new features and the tree was still dripping in gore - that should not be possible.
Then I remembered that 'split feature' (used later for a shell workaround, NOT for saving out parts - god knows I won't risk that!) is sensitive to the show/hide state of the bodies it splits.
When I rolled back to add features, I hid some of the solid bodies so I could see what I was doing. I didn't think to show them again before rolling forward. So the split feature did not have anything to work on (since it can only work on visible items), it failed, and everything else below it failed.
Just a heads up - split feature is useful for taking one body and making it into two, but it has the odd (and I think, singular) limitation that all bodies it works on have to be 'shown' whenever that split feature rebuilds or it doesn't know what to work on. This is in effect for every rebuild - ugh.
Thought I would share - a second's revelation saved me an hour or two of dead-ends, and maybe it will do the same for you.
Ed
BTW - the shell workaround: I do the classic shell diagnosis of cutting away parts of the model until the shell works -whats left is good, what is cut away is your problem area. Sometimes, I find that if I flip side to cut on the diagnostic cut, the other side shells too. SWx can shell each portion individually, it just can't handle the whole. So I use my cut line (using split part) to split that part into two bodies that CAN shell, then combine-ADD them back into a single, shelled body. Its realy bizarre, but it works.