I don't know the cause or prevention of bubbles. I've been pumping for 20+ years, and bubbles just happen sometimes. I've read many ways to keep them from happening and tried them all. Bubbles appear out of nowhere, I've seen them in my line when I never saw one in the res! I do a bubble check every day, and when I bolus, I check the line. And then just prime it out when I discover one.