Two years in a tent and it outgassed under 4 oz glass?

This is the only place where the doug fir outgassed under the 4 oz cloth, and actually bubbled up the glass! The cathedral tarp does barely touch this area, and it has gotten over 120F in there, but the other side, right next to this, had no such problem. I hope the caprails do not do this anywhere else in the summer heat and sun.