My son bought a 8-year old house, last August, that had some new "plastic" flooring put in the basement over concrete in preparation to putting it on the market by the previous owner. I'm guessing that was done within three months of him buying it.
Just yesterday, we went in the basement and we noticed there is a crusty thing that 'oozed' up between some of the planks. Not everywhere. Just three or four places as shown here.
That image shows it being flat but one of the others is humped over like it had bubbled up. I ran my finger over it and it's a dry crust that just crumbled in place.
I don't know if that could be an adhesive or fungus/mold or even dog pee (he swears it can't be dog pee).