It's the solvent in lacquer that is "hot" and will cause the lifting. Once the solvent evaporates off then painting over lacquer shouldn't cause lifting. The other way round, lacquer over enamel, if the enamel isn't cured hard the solvent could/will bite into the undercoat and lift. That's why lacquer thinner is used as a gun cleaning agent, because it's so aggressive, though if a catalyzed usethane has kicked even lacquer thinner probably won't break it up. Couple things might be going on here. Because of VOC regs, the thinner in the lacquer you're using is minimal thus flashes off faster than it can attack, and/or you had sufficient heat to draw the solvent off before it could work down.