White Labs WLP568 Belgian Saison Yeast Blend

Ripped through a 1.065 OG Imperial Saison down to 1.004 in about 6 days. Racked into 10 lbs (2 lbs/gal) of Sangiovese Grape Must, which brought it up to 1.024 and it ripped through that back down to 1.004. Sometimes Saison Yeast is known for stalling,but with a stay temp ramp from 68 (held 3 days) up to 78,it kept going steasy until terminal gravity. Ended up with a 9.2-.6% abv in about 2 weeks. Letting it clean up now.

I used this yeast to ferment the Petit Saison d'Ete extract kit from Northerb Brewer,O.G. 1.040. Pitched 1 vial at 70 deg. F. Fermentation began at approximately 12 hours in. Slowly raised temp. over first week to 80 deg. Held at 80 deg. for second week. No sign of fermentation at day 12, F.G. 1.008. Bottled at day 14 to 3 volumes in 22's. After 2 weeks of conditioning the carbonation is perfect, the flavor is as expected but there is an off aroma when the beer warms to 50ish. I would describe it as a slight onion smell. Possible contamination or perhaps conflicting esters form Saison yeast and Belgain Ale yeast?