What kind d of heat sink do you have on your controller? Pictures help a great deal. Your controller must have a good heat sink to sink away all the excess heat or you will get your controller to either go into cutback mode or just plain kill it.I have been gradually increasing the number of cells in my battery pack. I was advised, and subsequent experience showed, the controller could handle up to 120v dc even though it was 96v nominal.
Once the pack voltage got up to 112v, I had one instance of thermal cutback due to the controller overheating on a very hot day (39 centigrade).
When I added another two cells to get pack voltage to 121v I bought a 120v controller.
I had been advised that controllers can handle marginal over-voltage whereas motors can handle somewhat more over-voltage.