if w != (vmax && vmin)
compares w to a boolean value of vmax && vmin, and because w, vmax and vmin are all numbers it naturally doesn't work.

first, this is NOT an issue. It's just a question.
for your question, my answer is: perhaps you should not using delete in the map! loop. I guess it will skip some index(I'm not sure. because I don't know Ruby and I've not try your code)

delete mutates the original array, and in general putting side effect code inside a pure list method (map) is never a good idea.

After each deletion the elements after the deleted one are shifted and the indices get offset too. It's not a kata issue. BTW, modifying input in-place is usually not expected unless explicitly asked for.

Oops, you put a double equals instead of a single equals. Change counter == counter + 1 to counter = counter + 1

Actually, your code is wrong. You need to change your break statement to counter == n+1 or need to put your counter increment after your break statement.

Your counter variable exceeds the value of n. This is the reason why it takes so long, it's because you end up with an infinite loop, since it never reaches the break statement.

Example

power_of_two(0)

loop do                  #first loop
  counter = 0 + 1
  
  break if 1 == 0
end