Hi. What exactly is the problem with the while loop?

Already answered in your other post, the problem was you used elsif there:

elsif

ns = 0 # this is line 7

There it was your = in a conditional
The current code works (see how you use proper markdown so your code doesn't lose indentation and such).

1. This is not a bug, but issue with your code
2. Yes, you can leave your solution under a spoiler tag if you need some help.
3. You are not providing your whole code. You excluded beginning and end of the function (though when you asked this question on forum you posted the whole code, not part of it), because of this we can see a correct loop, but we can't see your elsif right before the loop which has no condition to be tested on.

Also here it can't be marked as containing spoilers.

elsif

ns = 0 # this is line 7

There it is your = in a conditional

Is this a bug?

This is asking a wrong question in a wrong place...