Bubbles or missing areas when printing

[tcwaters]

I'm having an issue where, when I pull the squeegee sometimes there will be small and sometimes large areas where no ink goes through. The areas where no ink goes through always seem to have clear distinct boundaries, like it is an air bubble or something. Am I pulling too quick? Have a bad squeegee? Not holding the squeegee at the right angle? This is les if my flooding of the screen is good, but even then, it can happen. How to minimize or eliminate this? THX