@Nicolas LEDUC
I understand your are upgrading your AKS cluster from v10.1 to v10.2. The upgrading is failing and rolling back to v10.1 automatically. Please correct me if I am misunderstanding the issue.
This can occur if you do not have enought compute quota during the process. Please check your quota and request an increase if necessary. For more information on the process and steps please refer to the Upgrade an Azure Kubernetes Service (AKS) cluster page.
Hope this helps! If you are still facing issues please let me know and we can investigate with you further.
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