Sometimes, Unicode-Unihan installs normally. Sometimes, it seems to take forever. When I look into that I tend to find it's sitting at "Preprocessing source text" and that the FennIndex.db file is enormous. I just killed the build after waiting a few minutes and found a 12 GB file.
From @rjbs on rt.cpan.org (https://rt.cpan.org/Ticket/Display.html?id=125834)