Hi,
For the best part of a year now I have had a flow running hourly that has concurrency control enabled and set to 1. It has been working fine as is however there have been the odd occasion that I have had to manually trigger the flow using the run command/button. For some reason when I have done this today i get the following error appear and cannot seem to get around this:

Just to clarify if I leave the flow it will trigger and run correctly so I know there is not a problem with the flow.