I think my assembly is finally ready for the bit bucket. I tried to replace components on four screws. Two were mirrors (why do people do that?) and Replace Components wasn't working right, so I just deleted the four screws, and put the four correct ones back in. Now I see all of the original screws have gone missing, and when I tried to add one back in, it shows up in the feature tree, but I can't see it in the assembly, even if I isolate it. Even if I rebuild it 20-100 times, too. And mates have gone red (among other things). These are just some of the most current troubles I have with this assembly. I really don't want to start over, because the first time took me three days.