I purchased my Curvy 8770 almost 5 years ago and I just love it. But recently, for some strange reason, the new 15J bobbins will not slide all the way down the little post to fill it. I bought two packages, two different times recently, thinking maybe the first purchase was flawed, but the second time I had the same problem. It only goes about halfway down the post. My filled bobbins work fine, they slide all the way down, but I've had them for years. Any comments or suggestions?