I had that happen to me before, i was feeding my male Argentine boa and as typical argentines (very agressive feeders ) he missed his prey , bit and threw a coil around himself . i waited a few minutes nudging him but like Sleepy Panda said they just tighten there grip even more..its an instinct thing i guess . I sprayed him with water and he let go almost immediatly then fed and slithered off onto his hotspot .......god i miss those guys