Maintenance- You cannot delete resource instance as it is already used in work execution.WIS-4440379

Summary:

Unable to delete a resource instance (labor type) from Manage Maintenance Resources.

We created two Resources of type 'Labor' (Resource A and Resource B) under Manage Maintenance Resources. And each resource is associated with 3 different resource instances each.
While trying to add the resource instance, we accidently provided a resource instance in Resource A instead of Resource B. Although these resources are not utilized in any Work Order, we are not able to delete the resource instance. The error is "You cannot delete resource instance as it is already used in work execution.WIS-4440379".

Is inactivating the resource instance at Resource A an only option to add it in Resource B?