You are absolutely correct. It is weird that the problem only occurs with one of the tests instead of all of them, but not mutating the input solved the problem nonetheless!

you are mutating the input array, while the tests re-used the same arrays for several tests. I fixed the issue, but in general it's considered bad practice to mutate your arguments for no good reasons; and on Codewars it might confuse the tests suite for some old katas

As previously mentioned, the Glider 4 test in Python expects an incorrect result, making the Kata impossible to complete.

The expected result in Glider 4 has untrimmed empty rows and columns.