I am not sure but if you already water tested it and it passed with no issues, then my thoughts are from having the 2A & 4B-T that when I am outside in the sun for longer amounts of time wearing the t-dials, when I come in they do appear to darken a bit more which from what Markus Tschopp tells me is how they develop more of their patina......i.e. baking in the sun. I would be careful not in wearing them but how much you wear them outside in direct sunlight for extended long periods of time. I am no expert but I fear and guess that with the development of the patina which is very cool there is a point where the dial can become too baked and maybe that is how flaking gets started.
Let me know, I am curious to find out what it is.