Queue Won't Round Robin Right

I’m trying to setup a new queue for a New IVR, but whenever I select round robin the first phone that gets the call rings until it times out (15 seconds) and then it barely rings on the next phone before going back to the original phone and ringing for another 15 seconds until it times out again. Then it goes back to the same phone that barely rang the first time and barely rings again and then back to the original phone for another 15 seconds. It keeps doing this until the queue reaches it’s Max Wait Time of 3 minutes. The only work around I have is to use ‘ring all’ which isn’t exactly what the manager wants for this implementation.

Does anyone know what would cause this and how to fix it?