When it comes to offset Screen-Printing, keeping layers of color perfectly aligned (registration) 100% of the time is next to impossible.
If misregistration is an inevitability, how can you combat this and keep your artwork free of odd separations and white gaps?
1. In your initial design, create barriers and significant separations between adjacent colors that could potentially become misaligned.
2. The second answer is a method called Trapping. This process involves adding an extra stroke around letters or shapes to create coverage (called spreading) and print over exposed areas. If you're not comfortable with the visual outcome, try using a black overprint stroke in its place.