I had this happen to me. I was told by the dealer that I wound the bobbin too fast, (it was embroidery bobbin thread). This created too much heat and expanded the bobbin. I removed the thread onto a spool by hand, took off the bobbin. Viking bobbins are plastic. Then compare it to a new bobbin you could see the difference in the size. THROW THAT BOBBIN AWAY!
At retreat this week, I was telling the story to another lady. Wouldn't you know it, someone else had this happen and that lady I told the story to was nearby and helped her. That time it was sewing thread that she was winding.
Moral of story, slow down.
Jean