Clearly this an issue with resin in the open strip joint and not expanding air in the wood fibers, since your surrounding wood is free of bubbles or pits.

If you had expanding air off gassing from the wood cells, or seam voids, with rising room temperatures your epoxy will create bubbles, which often don't burst and which turn hard as the epoxy cures.

With a wet-out of cloth over dry wood there is always the potential for parts of the wood to absorb more resin starving the cloth. This is a good reason to do a seal coat of the wood first, then after the wood surface is tack free, lay out your cloth and wet-out separately if you want a transparent exterior layup.

What you have appears to be resin which filled the gap in your wood strip, (after it looked okay and you left for dinner) which later absorbed into the wood in the sides of the gap leaving the resin sucked out of the gaps between the glass cloth weave creating tiny holes.

Unfortunately the physics of surface tension are working against you and you will NEVER fill those holes. Try for a few hours and you will agree. Ask me how I know.

Your choices are to carve them into a groove which you then may be able to fill, or to sand the glass off in those spots and hope a new layer of cloth applied while room temperatures are dropping.

Or pretend they don't exist and see if the wood turns dark from moisture absorption.

Sorry to be the bearer of bad news.

Good luck!

Rob