I generally like the Vallejo product line, but their gloss clear is the worst clear coat I've ever tried. Their semi-gloss and flat clears are fine, but the gloss is a mess waiting to happen. Go figure.

In general, clear coats are a bear, and an unfriendly one at that, because it is hard to see how heavy a coating one is applying. Working with a light source at an angle to the surface, one can sometimes judge by the surface glare how thick the coating is.

Now the real joker: Just because an acrylic coating is water based does not mean it will not be attacked by other solvents. When in doubt, test this on scrap, not the model you've been working on for a month.

Also, gloss paints in general cure more slowly than flat paints, so give them more time to cure.