I often have same problem. Somewhere else on this site a few of us have discussed getting large bubbles in the insulin reservoir. Check yours to see if you get them, several times a day, say each time you bolus for a meal. if there is a big bubble, you need to disconnect from the inset and pump the bubble up through the line. I theorized how the bubbles get in there, and I am still a bit stumped. I just know this, and I use Medtronic, the reservoirs are plastic which attracts tiny air bubbles to the inside surface of the reservoir, almost invisible to start with. The O-ring seals at the bottom of the reservoir on my pump are round cross-section but the area in which they are inserted are square cross section. I think that is problematic; I also notice that after a day, small bubbles collect along the inner surface of the O-ring that touches the insulin inside the reservoir.
I raised the issue extensively with Medtronic, but they keep ducking the issue by blaming it on me, nicely, or just not replying at all. So I filed complaint with FDA, who oversees the pump industry, and they included it in their system. I do not know what they did with it, but others have also filed similar complaints. I googled bubbles in insulin pumps and got many hits, particularly in Europe for some reason.
I think this problem is endemic in the plastic reservoirs. The round O-rings in square cutouts can’t be good, and is a terrible design. The rings should have square cross-section. Also the soft rubber makes it easier for the ring to distort and let air cross the boundary. There is also the problem of diffusion, which can allow a gas cross a boundary into a liquid under higher pressure. It goes against common sense, but is a well-explained phenomena in chemistry.
If you find the bubbbles I recommend reporting it on this site in the appropriate place (search for air bubbles) and complain to
Animus, and if they do nothing, complain to FDA. the problem needs to end.
Finally, make sure you don’t draw cold insulin into the reservoir when you fill it; bring it to room temp first. And make sure to tap out all air bubbles. As I pull the inner piston of the reservoir back, I also rotate it, which seems to bring up air bubbles. I do that just to make sure I am wetting all the surfaces.