: Here is another photo of the problem

Good pic. Notice how the bubbles line up with those strips.

Wood is a lovely natural material which contains air and moisture. When you seal that under epoxy you create a pressure cooker. The air and moisture in the wood heat up and expand. If the epoxy is warm and/or soft that expanding air or watervapor can create bubbles just like you have.

Just from storage some strips will have a higher moisture content than others. Or, a board might get wet weeks before it is ripped into strips.

The good news is that when you do repair this area the epoxy now in the wood will provide a superior seal and any moisture that has escaped will not be getting back into the wood--so you won't have the problem again.

Considering the area involved you might want to remove the existing glass with heat rather than sanding. Warm the area with a heat gun or an electric clothes iron (cover the area with a piece of aluminum foil so the iron doesn't get wrecked) then while the area is hot slip a putty knife between the wood and the glass/epoxy.

Good luck with your future repairs.
PGJ