After raising this issue with Microsoft, their backend team concluded the following:
The investigation revealed that on 2026-03-17, there was a transient fault in one backend instance of Azure Resource Manager (ARM) caused failures for any CRUD operations routed to it, while other instances remained unaffected. The issue was detected and resolved automatically after the instance restarted. No configuration changes or deployments triggered the problem, and it was confirmed to be an isolated reliability fault.
To prevent recurrence, the platform team has filed repair items and is working on a fix, aiming for global deployment by May 2026. We apologize for any inconvenience caused.
Mar 26, 9:24 AM