Ah that's not good reading about your chrome box! Such a shame as that box would have looked amazing if it worked.
I haven't had time to do anymore testing yet, but I've got a few theories. My red boxes don't look as bad as your one, I just tried to catch the marks in the light as best as I could. I've just looked at some blue boxes that I did, and you can barely see where the decal was. Also, there are none of the water type marks on them. A lot of my powder came from a local powder coating company that was throwing out a lot of their old, out of date powder (although it was stored correctly so it's still good to use), the issue with this is there could be different types of powder that I'm using, so unfortunately I can't test the different types of powder theory. I'm going to paint up a few more scrap enclosures in the red powder and use your suggestion of the hair drier to see if that works on them. Thing is, the blue enclosures I used the same method on and they turned out as close to perfect as they could be.
After putting the decal onto the enclosure, I then just put them straight into the oven for 10 minutes, but I've had massively varying results. With the hair drier, did you take the label off when it was dry then put it in the oven, or leave the decal on when it was in oven?
I'm in the process of making a few drilling templates so I can get a bunch of enclosures drilled and then coated on my days off. I've just got my new powder coating gun, I just need to get some fittings for it then that's good to go!