SharePoint Task List Project - Unable to filter certain tasks from view

Hello everyone, 

I have a SharePoint task list project. On the task list I created a view that filters out tasks that are 100% complete. The filter works on all completed tasks with the exception of one. I have tried using different filter criteria (such as 'completed = no') to no avail. This one completed task in particular refuses to be filtered out of the view. Has anyone encountered an issue like this before?