Strange odor - strange happening

I had an innerestin' thing Friday. A couple of weeks ago, I brewed a 10g batch of my kolsch. Same recipe that I've done numerous times, hit all my numbers, all went well. Friday, I cracked open the buckets and the smell 'bout blew my hair back! It was a VERY pungent, cidery-solventy hot odor. It was in both buckets, but the 1st was much stronger than the second. I thought the batch was ruined. Then another brew buddy showed up and I opened them again to show him, but the smell wasn't as strong. Another guy showed up a couple of hours later, and when I opened them the third time to show him,the smell was almost gone in the 1st bucket, and was gone in the second. I've never gotten this odor before. Is it a case of some volatiles being trapped under the CO2 and not being able to escape the airlock?

I'm going to check it again this evening (if I have time) and see if the odor has returned in strength or dissipated further.

For ref, I bittered with Magnum, flavor/aroma are Tett. S-05 yeast. Beer looks very clear, with just a few flecks of schmutz floating on top. It looks like my kolsch always does.

Well, I checked it and it tastes OK, still pretty green even for un-carbed beer. But the smell is still there. Still very strong. I'll check it again in 2 weeks.