Any time I try to perma-delete a page that is in a category, it throws a "Wikimedia\Rdbms\DBUnexpectedError" exception. Possibly because the extension does not remove category associations for the page (?).
This is also most likely the cause of the problem many others are having, where certain pages work but others don't (see below).
Temporary work-around: manually remove all Category tags from the page before perma-deleting it.