Earlier this year I changed from a 26er to a 29er. I moved my XT drivetrain to the new bike, but kept the Sram x9 direct mount FD since the old bike did not have a direct mount FD. Chain rings are 28/40.

I keep having problems with the chain dropping off the big ring. It usually happens when I coast through a rough section and then try to put down some power. Usually I loose the chain on the outside. I brought it by a shop who said the cable was a bit slack and also adjusted the limit screws, but it still happened. I took it to my normal shop and they discovered that a section of chain links were twisted. They replaced the chain and adjusted the FD, but it still happens.

I know they are supposed to be compatible, but could it be a compatibility issue with the Sram FD? This never happened on my old bike with an XT FD (not direct mount)

Does anyone have any ideas before I start swapping parts?