What´s mean "A workflow is currently running. Please wait for it to complete", why happen this situtation??? What´s is the workflow running limit by item?
I dont know.
Is it a List or Site workflow and Is it having any sub workflows? Can you try to insert 'Terminate Workflow' action in workflow. And also ensure to terminate all failed instances of that workflow if any. As per my knowledge on a same item, you can have 3 instances of same workflow.