Can you try to use this command, maybe there aren’t enough permissions with cochpotato and use it on your Movies and Completed Movies folder.
I totally missed your folders permissions, it should be like you have it in folder Series:
drwxr-xr-x 11 osmc osmc - Movies
drwxrwxr-x 2 osmc osmc - Series
That means, root user can read,write and execute.
But osmc users can only read and execute. And the same for everyone.
Root and osmc users can read,write and execute, but everyone can read and execute.
This is how it should be, because couchpotato runs with user couchpotato, which is in the same group like osmc.
Root|osmc|everyone (7 7 5)
First letter d is for dir aka folder.