I have three S9's, they all run comfortably under 100 except for one... This one has a hash board that runs at least ten degrees higher than any of the other hash boards... Thought it was a little odd, i had to under clock it two steps to get the temps under 100.
Sounds like you have one or several alu cooling finns thats not glued perfectly. It's a easy repair and you are able to buy cooling glue with good sepcs cheap on e-bay. Just remember to let them sit for at least 24 hours before you raise the hash board vertical for installation in the miner. Just remember to be careful or let someone with PC skills do it for you. I think I did see some guides on YouTube.
I was thinking it could be something along those lines... i'll wait another two months before cracking the bitmain seal so i am out of warranty. I figure it cant be all that complicated, i've built many a pc's so i'm familiar with the concept. Is there a preferred brand of cooling glue that you know of? What about cleaning agent to remove the glue residue once the heatsink is removed?