Adding Custom Metric to Existing Folder Results in New Folder

Adding a metric to an existing folder results in a new folder with the same name.

I have created a custom metric from the Data tab. When I begin typing the folder name to add the metric into, the list appears. If I choose an existing folder, I would expect the metric to be added to that folder. Instead, a new folder is created with the same name as the existing folder.

Thanks,
Nathan