Tray 27 started off quite painful. From what I remember with the Clincheck, now that my formerly-crooked right lateral incisor is in line with my central incisors and left lateral incisor, those four teeth are moving backwards in my mouth the next few trays. I think that's where the pain was coming from, because my lateral incisors were sore. Not fun. But at least it subsided after a few days. And it wasn't THAT bad, just comparatively more pain than usual.
My teeth still aren't tracking like they should (as you can see in the picture - the gaps below my right central and lateral incisors). In fact, the end of the left side of the tray wouldn't stay over the molar for the first few days. I kept biting it down. It's finally settled, but it was stubborn!