It's hard to reply this. Because im in the same place as you. The last one fails for me. I digged a little bit and I ploted into a scatter graph, but it makes me more disappointed (at least for me) because seems like there are not visible clusters there.

You can print things to console. Here's an example in Python: https://docs.codewars.com/training/troubleshooting/#print-input

fib(-91) = 4660046610375530309, not a kata issue.

Whether there is an issue or not, this isn't the way to describe it.

Which language? Which random test? What's the issue with it?

Oh right, none of that is provided, so... closing.

so you're saying there's no issue?