Errors in backup

Hi, when trying to backup I get the message

[critical] – [2023/07/28 13:16:38] – We cannot proceed, as we could not write files to disk. It is likely that the server disk is full, the maximum number of files were reached (inode limit) or there is no write permission to directory wp-content/uploads. Please free up disk space on the server or correct the folder permission to 755.

We verified that the suggested fixes are not the issue. How else can we troubleshoot? Backups were a primary reason we purchased WP Staging Pro