Completed Items Reappearing

I've been extremely frustrated with To-Do since I was forced to use it for my personal list over Planner, but now it's completely unusable. Now any changes I made are going right back whenever I refresh the page or leave and come back. Completed items are undone, changed due dates are reset. Even new tasks I add are gone.

You can see a video here: https://share.vidyard.com/watch/sNdBqnkcD2zb7BiwRoGqyt