@Qifeng Hou ,
In Azure Kubernetes Service (AKS), planned maintenance is performed during the maintenance window that you specify when you enable auto upgrades. If the maintenance is not completed within the specified maintenance window, it will be rescheduled for the next maintenance window.
If you have chosen the stable auto-upgrade channel, the upgrade process will be slower and more cautious. It will only include updates that have been thoroughly tested and are considered stable. If you have chosen the rapid auto-upgrade channel, the upgrade process will be faster and may consist of more frequent updates, including updates to API group versions.
Regardless of which auto-upgrade channel you have chosen, if there are problems during the upgrade process, such as API group version updates, you will receive notifications through the Azure portal and email. You can also monitor the upgrade process by checking the upgrade logs in the AKS cluster resource.
I hope I have answered your question.
----------
Please "Accept as Answer" and Upvote if any of the above helped so that it can help others in the community looking for remediation for similar issues.