First let me say that when I paint over a powdercoat base, I use top quality (=expensive) automotive paints. These differ greatly from rattle can paints, and need different prep to work properly.

So, to address ChillGreans situation...which I agree, is hard to describe.

Might be that you didn't sand the primer before spraying the color.
You can also scuff with a fine grit ScotchBrite pad. Just enough to break the surface and give the color some tooth.

Might also be that you don't need primer to shoot black rattlecan paint over a powdercoat base.
In which case, you could rattlecan clear the whole frame, once you've done the lugs black.
And if you've redone them a time or two, that might be a good thing anyway.
Or just shoot the black, no primer, and call it good.

UNmasking is another area of interest...
Some say unmask while the paint is wet so that the wet edge "heals" itself a bit before hardening.
Others say wait until the paint is fully dry and the edge will be clean and sharp.
I've tried both ways.
Success & failures either way.
Having a fresh sharp #11 Xacto blade handy helps.
The thing to look out for is, the paint coming off with the tape and pulling off pieces of the paint you want to keep. So you use the #11 to surgically separate the paint at the edge of the tape.

Might also be that you need to spray a thicker, wetter coat of paint.
The first coat or two can be light, but to get that wet glosss look, you need a medium heavy coat so it flows out all smooth & shiny.

Might be that someone nearby shot some WD40 and some particles blew onto your frame between coats.
That would cause the notorious fish-eye effect. Lots of little fisheye dots in the paint.

Without detailed close-up pictures of the problem, I can only guess though.

My money is on..."Thicker, wetter, final coat of paint".

But check with the powdercoater and see if he/she has any insight on rattle can compatabilty with their powdercoating.

A final thought...you could probably get away with doing the lugs witha nice 8-10 dollar paintbrush from the art store. One-Shot Sign Lettering Enamel is one of the best paints. (Better than Testors model paint)
If you have gone to all the trouble to mask, it should be pretty easy to get the black on with the paitbrush. Same trick applies, try to get all the paint on the lug quickly enough that all the paint is wet at the same time. This allows for flow-out and produces that nice shiny gloss.
This may be one of those times to UNmask while still wet-ish.

Good luck & let us know the final result...ie; PICTURES! Please.