Task not claimable, task slot broken

I wanted to claim a completed task and while completion, I got network errors.
Since then, the completed task stays on my list, disappears when clicked, but don't moves to the catch screen.
After leaving and re-entering the task menu, the same task re-appears with the completed coloring.

Now, I'm stuck with only two functional task slots.

TheSilphRoad: please help.