React: why is the mini app not working correctly?

Question

React

Good afternoon! I understand React, I wrote a mini application with tasks: https://jsfiddle.net/47tfojLa/
But for some reason it doesn’t work as it should, although in theory it should work as it should, namely:
When you click on the button, delete the task, the task should be deleted, but in fact the last one is always deleted, even if you delete the first one. I've already broken my head with this error, there is very little code, and as for me, everything is fine with the code, but the application behaves incomprehensibly ...

Answer 1

https://jsfiddle.net/47tfojLa/1/
Don't use indexes as keys