Only the last 3 days of snapshots are saved, but the problem happened more than 3 days ago. I could revert back to the original installation snapshop, but I lose a lot of configuration work. So, while the solution you propose will work, it's not practical in my case.
Can you propose another method to delete a partially-off-screen fence?
Also, if I wanted to increase the default # of snapshots saved to more than 3, is this easy to accomplish?