I don't see anything odd about your rim that would lead to tube damage; however I have had this mystery situation as well. Have you checked for any sharp spots on the offending nipples? Dragging a microfiber cloth over them would tell you. Still, you would expect the rim strip to take care of most flaws. I have 2 recommendations that worked for me: 1) try a wider rim strip. Sometimes narrow ones move to the point where the nipple head is partially exposed. 2) install a wrap of filament reinforced packing tape tightly around the rim before you add the rim strip.