Scrivener autosave failing to write to memory

I keep getting a message from Scriv3 on my Windows 10 computer telling me it cannot save (in progress backup save) to disc due to write access issues, advising me to Save As a new project.

Can anyone advise? Is it a Scrivener issue or a W10 issue is the first question.

Tell us more about where you are trying to save it to. Is that location a OneDrive/Google Drive location?
Write access errors typically occur because more than one process is trying to take temporary control of the file, such as might happen if a file sharing service tries to interact with a Scrivener file while Scrivener is expecting exclusive access.

It is to a root directory but that directory is shared with OneDrive and also on a frequent back-up schedule to Dropbox…

If by “a root directory” you mean the root of the C: drive, then permission problems could be intentional on the part of Windows. Microsoft changed the basic security of C:\ because of numerous reports of users causing unintentional damage, and also as another safeguard against malware gaining some control over the system.

In general, it is not a good idea to write files to C:\ , though you are allowed to create folders. Your Users subfolders and other locations are meant for safely storing your files.

It seems like trying to write to C:\ while also having OneDrive and Dropbox needing access is just asking for trouble. Have you seen L&L’s notes about using file sharing services at https://scrivener.tenderapp.com/help/kb/cloud-syncing/using-scrivener-with-cloud-sync-services ?

In addition to the location issues others have brought up, you may need to double-check your anti-virus/Internet security settings. Depending on what apps you are using for these functions, they may not be letting Scrivener write to the disk in those locations. Many Windows Scrivener users recommend whitelisting the Scrivener app/application folder in your anti-virus app and/or Internet security app (and optionally, Windows Firewall) so that they don’t try to perform those real-time scans.