Thank you for reaching out & I hope you are doing well.
Based on the information that you have provided; you are attempting to restart your AKS cluster but failing with that error message. From that error message, I am concerned about this specific part:
/subscriptions//resourceGroups//providers/Microsoft.Network/loadBalancers/ has two child resources with the same name (28548feb-70a2-4779-8711-89becdd51691)."}]
I suspect that this 28548feb-70a2-4779-8711-89becdd51691 is pointing to the name of a public IP address of your Load Balancer under Frontend IP Configuration, e.g.:
Doing my research, there seems to be a very similar error message described in the following external StackOverflow link:
Can you please check if you see a duplicate name or IP in that section? Your Load balancer resource should be under your MC_Resource Group.
From the StackOverflow link, a workaround is removing the IP configuration to resolve that duplicate conflict.
Please "Accept the answer" if the information helped you. This will help us and others in the community as well. Feel free to reply with any other questions or concerns.
Hope this helps!