to recreate this problem:

1. create a new page in some space "A"
2. create a new task on that page, assigned to me
3. save the page
4. move the page to another space "B"
5. go to the Tasks page of my Profile
6. notice two things:
a. the task is listed TWICE
b. NEITHER task can be closed from the POV of the Profile/Tasks page. Clicking the checkbox next to the task appears to close the task; but when you refresh the Tasks page, the task is once again unchecked.
7. However: when you view the task from the page in space "B", it is marked as Closed. (checked)