I'm getting a long delay either when opening Manage Authors from the Tag Browser, or right-clicking author in Book Details -> Manage. This happens only on my main library, which is the largest one.
Upon a reinstall of stable version 6.29, Manage Authors will open instantaneously, as with my other libraries.
While troubleshooting this issue, I think I found something worth looking:
The message above happens when doing a database integrity check with the option 'Also compact the notes database':
This happens on the other libraries, as well as with an empty library I've created for test purposes with the default structure.