Heartbeat package generated from Azure App Service not necessarily has the correct information about resource group:
Current implementation relies on the format of the WEBSITE_OWNER_NAME environment variable exposed on App Service: 'subId'+'resGroup'-'location'webspace, but there can be cases where 'resGroup' is not the name of actual resource group. For instance names don't match after resource was moved to the different resource group, in this case WEBSITE_OWNER_NAME is not updated.

Recently App Service exposed different variable that we should add to heartbeat payload and use it for resource group identification: WEBSITE_RESOURCE_GROUP