I just bought a Native American flute and it plays beautifully with one problem. When I remove the finger from the bottom hole, sometimes there is a loud squeaking and the flute goes high pitched. I played around with it and sometimes I can get the note I want, but the squeaking happens even when I make sure that all of my holes are covered and I am breathing slowly. It only happens when removing and placing my fingers on the bottom hole. Is this user error? I can’t seem to keep it from happening frequently.