Really weird... The assembly has a mirrored sub-assembly. I then opened the original, un-mirrored subassembly and added some parts. SW wouldn't let me back into the main assembly, complaining about a component in rollback state. Couldn't close the main assembly, and couldn't exit SW. I had to kill it from Task Manager.
Any idea what's going on? It's one thing to not update the mirrored subassembly, but it shouldn't invalidate the main assembly. It's fine after restarting SW, but missing the new parts on the mirrored side. It sure would be nice if SW would track things like this, maybe track the mirror as a configuration rather than a separate assembly.
In general, how do you make best use of mirrored components and assemblies?