Is this a cast iron Boss ?
In the aluminum Boss there is a spring ( # AR-49) that keeps the tension upwards on the take up lever, to keep this problem from happening. The cast iron Boss does not have this spring. I had the same problem with my cast iron Boss, so I odered a spring from Tippmann, drilled and installed a pin on the take up arm and installed the spring. No more loops and slack on the top thread.
Have a look at Tippmanns website and compare the parts between a Alum. Boss and a cast iron Boss and you will understand
/ Knut