Yeah, it's one of my favorites too! Found it at my local drugstore years ago, and now it's become even harder to find "in person."
I love Clubman Vanilla it always smells great. I did decant mine and I saw no difference even over time. It's great straight from the bottle.I just cracked open a new bottle of Classic Vanilla and smells great, even straight from the plastic bottle. It'll get better after I decant it into glass. But still, its fine as is. I've never had a skunky bottle. I don't know if you just got a bad batch or if there's some ingredient that's not interacting with your body chemistry well.