I experienced the same. To use a quick shortcut, I restored a backup of before the issue appeared.
- put the files that you moved back to the correct folder name as it was when working ok
- define a waste basket folder path
- add another series first and check if that updates without issues
- add the RD series again
- perform a manual import on the RD files that are in your waste basket folder
Now it should run fine. If not, reinstall Sonarr (and get a fresh database).
Don’t forget that it is all database driven. As soon as any path is missing, and depending on the programming of this, you can run into these kind of issues. No offense to the programmer of Sonarr, I really love it!
If you want to move files/folders, first remove the series including a ‘Delete Files’ so that database gets in sync with the action(s) that you do. You still have them in your Waste Basket folder from which you always can import them manually.
Btw: the most recent version of Sonarr is Version 184.108.40.20638
Mono Version: 220.127.116.11
Where did you download your **Sonarr version - 18.104.22.1689 — 27/11/2019 from???