There may be issue with portal UI.
Please try the same with Azure cli, please follow the below MS article.
Validate
To test your move scenario without actually moving resources in real time, use the az resource invoke-action command. Use this command only when you need to model the results without following through. To run this operation, you need the resource ID of the source resource group, target resource group, and each resource that you're moving.
Use " to escape double quotes in the body of the request.
https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/move-resource-group-and-subscription?tabs=azure-cli#use-the-azure-cli
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