When printing lots of white flash with colors on top, you may struggle lining up every color—although they do line up pretty well—and find that the white extends past the rest of the colors. Why? You're likely using outdated technology. This can include low-cost or low-volume mesh, a single-axis blade, and absurdly close off-contact distance.
The majority of white inks are not the idyllic cold-cream texture variety, so they force us to apply fluid compression with the blade. If said blade is a single-axis, the only recourse is to buckle it and run slowly. A slow speed won’t adequately thin the white while we “squeeze” it through the tunnels in the cheap mesh, which is forced against the platen. The buckling and low gap means all the “pressure” is on the platen with none left between the blade and the mesh where it belongs. As a result, the printing tension is so low that it allows the single-axis blade to drag the mesh in the stroke direction.
Most colors are more forgiving than white. Use a lower count and high volume mesh for your white, optimize the gap ~3/16” for >25N/cm² – 3/8” for <20N/cm², set the tension on the white 30 percent lower than the colors and use a bi-axial blade. You'll probably find that all the colors in your print now line up.