It seems to be possible to either fully corrupt the database or at least fail to open it correctly. So far I have only been able to reproduce this using the fedora packages. The codepath that validates the database name after opening the db catches that problem.
It seems to only happen on larger folders and I've seen it for sure on the completethread query.

At least once I've also seen a corrupted master-db (that holds the named db's) with mangled names, not sure this is related and I could also never reproduce it.