Thanks for the reply.
My daughter walked in the room and unprompted said, "it smells like old popcorn in here". So I am not thinking it was DMS but rather diacetyl I was smelling. I may have mistook the sweet, grainy, buttery smell for DMS. I have been lucky enough to avoid both until now. It is starting to dissipate though. My guess is the acidulated malt may have caused the smell.
After hearing this I did some research on lactic acid producing diacetyl, while the specific sub strain of lacto is not mentioned, there is overwhelming evidence of this. Here is one of the papers I found: