More information from Azure regarding the issue:
Service Issue NM_B-R80
Preliminary Root Cause: We determined that a code regression introduced during a recent deployment impacted multiple App Service instances within the region resulting in the service management failures.
Mitigation: We reverted the deployment to a previously known good build and rebooted the impacted instances which mitigated the issue.
Next steps: We will review deployment procedures to prevent future occurrences.