Quick Edit insisting documents are checked out before using feature

Hi

I have a site that is receiving an error when trying to save documents after using Quick Edit Feature.

After using the Quick Edit feature to copy data to other cells the user is receiving an error;

"The file "https://domain.com/site/library/document_name.doc" is not checked out. You must first check out this document before making changes"

Only the one site in our tenant is receiving the error. I have checked the settings and Quick Edit is enabled correctly.

Any help would be appreciated.

Thanks

Gary