Yep I have had that happen, just recently. It had nothing to do with a sharp object because mine loads at the top of the machine. I think the thread gets loose and it just goes out of control. It happened to me with a very fine thread. I removed that bobbin and did another one and it was fine. So, I will segregate that bobbin as maybe a bad bobbin. (probably toss it as I have lots) Anyway, it happens and as long as it doesn't do it every time or on a frequent basis, I refuse to worry about it! LOL