Legends P08 Blowback part ID help

I had a problem with several BBs getting caught up in the works and jamming the toggle. Also firing just one shot drains the gas cylinder completely. I field stripped the pistol removing the entire top barrel/slide/toggle. I notice there is a wayward o-ring/rubber band as pictured at the center of the mechanism.. Does anyone know where this thing actually belongs? I suspect it is part of the problem? Pics of a working unit would help. Thanks

luger band.jpg