Could simply be that there is some internal logic problem. From your screenshots it's apparent that in the areas where it doesn't render the angle of the hatching is almost equal to the curvature of the paths and thus the effect would not register an intersection there and simply pass through. If the letters/ words are all one layer, split them up into several layers and adjust the settings. Sometimes even tiny variations in the angle can make all the difference.
In addition to Mylenium's suggestions try animating overlap, angle, and variation by just a couple of tenths. Sometime just a slight animation of those properties will prevent holes from appearing.
Thanks. I split it up into several pieces and it fixed the problem