Report in incident workspace not filtering by current incident

Content

I have a report within a tab in a Incident workspace. It currently shows a chart and should be based on the incident it is within. It uses data from custom Contact fields on the current incident. The report has the Contact table and the Incident table joined by id.

If I put in a filter based on incident ref and hardcode in a specific incident ref then when I load the workspace that chart appears. What I want is for it to be based on the values from the customs fields on the incident the report control is in. If I put in a filter for incident ref and leave the value blank (or no filter at all) the workspace gets stuck on "sending"  when I go to that report control. I then can not save anything until it crashes with an error.