I purchased a Diamondback Release several months ago. I experienced my first flat on it the other day and I am having a helluva a time getting the tire off the rim. The tire is a 27.5 Schwalbe Hans Dampf mounted on a DB Blanchard 28R rim. I cannot get the bead to pop out with tools or even by standing on the tire and pulling upward on the rim. I’ve fixed flats many times and have never had this problem. It almost seems like the tire is glued or fused to the rim. Any suggestions are welcome.