The obvious frame "issue" is the less then cleanest brazing and clean up around that seat stay attachment area and what might be some slight undercutting of the seat tube at the top tube's underside (third photo). neither of these likely contributed to the powder paint from flaking off. No surprise that the paint would flake at the corners/edges of the stay eye. Powder doesn't like edges, it can draw back/away from them. Since there's no primer under the powder it's adhesion to the metal is less then nicely done wet paint. Without an etching of the surface (and having that surface truly clean, again look at the third photo) the powder doesn't bite into the metal as well as it might. Since powder is chosen for cost savings and not finished image some degree of "paint performance" loss can be expected.

Very well done powder coating can look and last really well. But I've seen far more poor jobs then best ones. Andy