The other thing that will do that is if you've threaded the wrong way. A FW threads right to left, and the needle has to be flat side to the left.
If the threading is wrong (I've seen it on 2 other machines that I threaded the wrong way i.e they wanted left to right and I did right to left) and they brought up 3 threads instead of 2. It was sure a WTHeck moment when it happened the first time.