I'm having a fairly consistent problem which involves a peculiarity of
my royal icing. My technique with cookies is to outline and then fill.
What often happens is that the narrow areas dimple or create a
sinkhole. The wider areas never have this problem.

I've tried thinner fill and "stirring" the tiny areas with a pin to
break up any possible air bubbles, to no avail. Whipping the royal with
my handheld mixer just before applying it still yields many sunken
areas but fewer sink holes.

Any ideas or suggestions?