I've never saw Jug' feel pain without either magic or mental intervention, nor have I ever seen him K.O'd w/o those two.
Is 404 the only issue you have to show him being knocked out by physical force?
If so, does this one issue totally convince you of his ability to be K.O'd?
I've heard of Jug' being taken down by a God of some sort by way of nerve pinching, as yet no one has shown me where or when or to the circumstances were at the time.
If this is true and then I dont have a choice but to concied to the fact he can feel pain.