I always believed enamel over lacquer was the wrong combo..
The only thing I can think of relates to the semi-gloss clear... I've had trouble with it, too, and it hasn't always turned out looking semi-gloss; perhaps because the aerosol has a tendency to spray too much material. The more you pile up, the shinier it gets. That even happens with Dull Cote. And the problem you're having certainly sounds like there is too much material there. I say give it a couple days to cure, and check it again. Are you sure the enamel was fully cured before you used the semi-gloss? You might also consider decanting and airbrushing it lightly the next time. I've been airbrushing Testor Dullcote lacquer over enamels for decades with no problems. And I thin it with cheap generic lacquer thinner, too. The trick with Dullcote is to lay it on in a "dust" coat. As someone said, lay it on thick and you can have problems. You guys may have found my problem. i am giving it a light coat and too much comes out. i will try even to dust it lighter. I stays a little tacky all the time...