I can close a task, no matter its progress (100% or 16% or 0%)
I can reopen a task
closing a task prevents any checker to do any action in the task
the checkers can still see the task and its records but the task is marked as closed (see Passports here):
the closed task's records don't appear in the search results, only in the (future) Advanced Search results (cf https:/github.com/ICIJ/prophecies/issues/55)
As an admin, I close a task: