Thanks for the report – as for a “piece of meat” being in the snorkel my guess it was probably more like dried congealed blood instead of meat. As for all of the other cleaning etc you provided us with a handy “how to” reference” manual and I thank you!
I really think you need to drain the “juices” out of the cryovac environment better before attempting the seal in the Drybag. The meat should be moist, but not dripping or sopping wet. With as many others here besides myself using a Sinbo, the problem you reported is unusual so that’s why I am leaning toward your meat being too wet to began with.