I'm building some walnut cabinets with flat panel doors. I used 1/2" plywood for the panels and everything went well until I was about to put on some poly. There is some bubbling of the veneer on one panel on one of 11 doors. The bubble looks like it extends to the edge of the panel, but is trapped in the groove. The door already has BLO applied. I'm not sure whether it bubbled before or after this, but I think I would have noticed it.

Outside of more insulation in the shop walls, so that the neighbors don't hear me screaming, I'm looking for suggestions to fix this.