I showed some photos of that flaw to the engineers at West Systems (Gougeoun Brothers) and they felt that it was likely an issue where the glass was stressed/fractured because there wasn't a good enough joint between the strips, and they moved when stressed.

In the tests Fine Woodworking did a few years ago I think Titebond III came out best in their testing because of its gap-filling properties. PERSONALLY- I use Lee Valley GF2002 glue. It does exactly what it's supposed to do, better than other things. It's not waterproof, but I've got some sticks that I glued together with it that I've been using as garden stakes for 6 or 7 years, and they haven't come apart at all. It doesn't work well on light wood, though, because it dries dark. I use TB II for light woods.

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