Deleted tasks still showing up in task report in UI

When I go to the "Task Report" page in the UI, it shows several tasks (many duplicated) that were deleted from a page "IS Repackaging Project Plan". I've confirmed that these tasks do not exist on that page. Additionally, when I pull my task list through the API these tasks don't appear so I can't even try to delete them through the API. What's more, when I try to close these tasks to get rid of them I get an error saying the change could not be saved (see attached picture).

Please let me know how we can get these old tasks and duplicate tasks removed from our task list. We recently started piloting the Confluence product and would like to use it for some of our project plans but currently task lists are not usable with this bug and we are having to use a second system to track these.