I can fill in more detailed background if needed, but the current situation is that we are unable to upgrade our site past 8.1.0. I think that multiple failed upgrade attempts over the past several months, and possibly incomplete restoring of the backups has resulted in some leftovers that are preventing us from upgrading, as well as interfering with a few other key functions like editing file attributes. We've gotten some help on the forum (https://www.concrete5.org/community/forums/installation/cant-upgrade-past-8.1.0), but I think we've hit the limit of our own abilities. So we are looking for someone very familiar with the Concrete5 database structure to help us figure out what's wrong and how to fix it. We are desperately hoping to avoid having to restore all the way back to the last known functional version, which was months ago, and would undo quite a lot of work. Thanks for your consideration!

EDIT: Based on advice from several people, we'll likely wait on this until 8.3.3 is released, which will hopefully address at lease some of the issues we've been having.