I noticed too on my chest piece that the worst areas for me was on my chest bone and at bottom of the piece above my breasts. I had a couple of other random places too but those seemed the worst.
This is what I keep saying. Everyone's all, "Oh, the sternum hurts/is damaged? That's normal." But no, the tail is to the left of the sternum, at the top of the breast. Getting these areas tattooed was very painful, as well. The Aqupahor seems to be okay. I put on thin layers and still do a gentle dabbing afterward for safety's sake.
This is the weird thing about getting tattoos. Even if you keep everything consistent (artist and his/her methods, your methods of aftercare, etc.) something can still be off for one tattoo when everything else you've ever had turned out fine.
This is the first time I'm hearing of this. Ha ha! Did not know that, but will most certainly keep it in mind for the future.