In this PDF white paper, engineers from drywall-maker USG provide guidance on eliminating screw bumps, a.k.a. "screw buttons." Not quite a full-blown "nail pop," the small raised mud-bumps over drywall screws were reported as a growing problem by drywall contractors in the Mid-Atlantic region (Virginia, Maryland, Pennsylvania, New Jersey and New York). who reported they appeared anywhere from a few days to several months after hanging and finishing the drywall.
According to USG, the problem arises from the use of water-based, low-VOC drywall construction adhesives that are slow to cure prior to finishing. As a bead of adhesive cures, the report suggests, it shrinks, pulling the panel closer to the framing, and if the screw divets have been finished before the adhesive shrinks, the movement pushes the dried mud out. It's unclear what conditions are causing the adhesive to cure slowly, but the report does identify several factors that could be involved. There are a few solutions, however: 1) do not use adhesive (and more fasteners); or 2) wait at least 48 hours after installing the panels before finishing (which is seldom practical); or 3) use a foam-type drywall adhesive, such as the Tytan Pro high-yield drywall adhesive. Similar to a foam-type subfloor adhesive, the bead comes out as a foam, which then collapses to a gel before you apply the panel without further shrinkage that might cause the panel to move.