It’s not normal, but I have see it a few times over my years of pump use. I have almost always used Teflon cannulas, so I don’t think it’s related to the Sure T specifically.
I have always thought it was just related to nicking a capillary during insertion. It can be a sign of a cannula in trouble though. So it’s worth keeping a close eye on BG levels to ensure insulin is still absorbing properly.