Templating, multi value problem

I don’t see anything strange in the dashboard json. Can you check the raw query that is sent to Graphite and see what value is being substituted in this query:

You can do that by following this guide: How to troubleshoot metric query issues

or if you have Grafana 4.5.0 or later then you can use the query inspector: Using Grafana's Query Inspector to troubleshoot issues

This might be a graphite problem. What version of graphite are you using?

Ref: https://github.com/grafana/grafana/issues/5936