Optimistic concurrency or a uniqueness constraint lost a race. This is the one 4xx worth retrying, but not with the same body: reload to pick up the current version, then apply your change again.
Related
- Errors - how to branch on
code, and what not to render fromdetail. - Problem catalog - every code, its status, and whether retrying helps.
- Troubleshooting - what a message in the product means.