Workflow loop still running even after end workflow action completed

I have a workflow with 2 parallel branches. 1 is a Flexi task and the other is an automated reminder that sends when the current date is past the due date. The automated reminder  branch is comprised of a loop of if the outcome of the task is still blank, then a run if the current date is past the due date. Outside of the run-if but at the end of the loop there is a 24 hour pause before it loops again to check if the due date has passed and the outcome is still blank. On the task branch, once the user completes the task and therefore fills out the outcome, there is a "end workflow" action that terminates the workflow and stops the automated reminder branch from continuing to loop. The majority of the time, this has worked completely fine. However, I've found one workflow instance where the task was completed before the due date and it shows in the workflow history that the end workflow action was completed as well. But, the loop is still running and sends a notification every 24 hours to the users that already completed the task. The workflow is under the completed workflow section of the workflow history but it is not idle as it keeps looping. Because it says it is "completed" the terminate workflow button is unavailable. Is there a way for me to delete this workflow instance to stop the loop from sending the notifications? Any assistance would be helpful