We have been running sprints for a while with no problem.
Start sprint-1, two weeks later close sprint-1 and start sprint-2.
Repeat the cycle.
We have been doing this for a while, so our latest sprint is sprint-16.
I wake up today, and sprint-17 has started, but sprint-16 has not ended.
I am not sure how that happened.
You can see here sprint-16 is not complete:

But sprint-17 is also running:

If I try to close sprint-16, I can't move unfinished stuff to sprint-17, as it is not an option:

So I guess my question(s) is/are:
How did the next sprint start without ending the last sprint?
What do I do now?