Not sure what happened but it did. I have never had a starved spot before. Always careful to make sure all the glass is coated. Doesn't matter, I ended up with two small spots on my deck.

I am thinking the only way to repair is to grind it down, removing the white glass. Then patch it with a small piece of glass, maybe some 4 oz and follow up with a couple of fill coats. Any better suggestions?

FWIW I watched it for a hour and then had to leave. A quick check just before I left everything looked good. Looks like these two spots may have been a little low and the glass just lifted or the epoxy soaked into the wood. I guess it happens to everyone sooner or latter.