Overheating International prostar

We have a 2015 International ProStar with a Cummins ISX motor. It started overheating last year and we had everything you could think of redone on it trying to fix the situation close to 8000 in repair. Finally they replaced a sensor on the left side of motor, something to do with the def. That finally worked for a while. Till it was sitting there running and the def sensor malfunctioned causing it to say def was extremely low, throwing it into derate mood. At this time the dozer valve, air compressor, inlet and nox sensors, plus the def sensor that worked previously. With no luck.
So first thing I noticed is the engine oil temperature will rise with the water temp following closely behind. I noticed i always smell the same thing when it has regened. Any suggestions? Could this have alot to do with the def system? Is it normal to have I'll temp rising and pretty much mirroring the water temp?