I was experiencing similar Adv. Dragoon pounce-fails for a bit, as well. My theory had to do with the Adv. Goon's faster pounce speed... At least I think it has a faster pounce, or is it just longer? Assuming that both Goon pounces take the same amount of time to complete after a fully-charged launch, wouldn't that mean that the Adv. Goon's pounce would have to be faster to travel a greater distance? Maybe I should just check the source... Anyway, I thought maybe the quicker pounce was simply throwing off my timing after spending most of s1 swipe-pouncing with my regular-ass Goon's slightly longer window before contact. Though if you're not a swipe-pouncer, then this really won't apply to you.
Side Note:
"Swipe-Pouncer" sounds like a type of rapist. But that's actually quite an accurate assumption. If you've ever played against a really good swipe-pouncer, then you know what I mean.