A 423 Locked error is a webserver’s code for: "The resource you're trying to modify is currently locked by another user or process.".

How do I fix or troubleshoot a 423 Error?

Common steps include reloading the page in your browser, checking for typos in the URL, verifying server status, clearing browser cache or cookies, and contacting the website owner or server administrator if the error persists.

423 Error | Error-Message.Net

A 423 Locked error is a WebDAV HTTP status code indicating that the destination resource is locked to prevent conflicting simultaneous edits.

When collaborative platforms or network file drives allow multiple users to interact with shared documents, the server places a temporary lock on a file while someone is modifying it. Other users attempting to write to or delete the file will receive a 423 Locked status.

Determining why

Another user or automated script is currently editing or saving the file.
A previous editing session crashed or disconnected without releasing the file lock.
An administrative file protection policy is active on the server.

Steps you could possibly take:

Wait and retry - In most collaborative environments, the lock releases once the other user saves or closes the document.
Check lock status - In WebDAV clients (or tools like Nextcloud or SharePoint), look for an active lock icon and check who currently holds the lease.
Force unlock - If a stale lock remains after a crash, administrators can manually clear active locks using WebDAV UNLOCK requests or server management consoles.

Source: RFC 4918 Section 11.3 (WebDAV)