I've had this, or a similar, issue before. When I looked at my flow runs there were several that we still noted as running from several days prior when they had evidently crashed or finished. Deleting them from the flow runs screen cleared them up. I'm not sure how it would work if you're on the free cloud tier and the crashed flow runs had dropped off the history.
I never worked out how the flow runs had entered that state and I'm not able to replicate. I just keep an eye out for them getting stuck again in future.