5035 sputters and stalls when warm. Blue/white smoke emitted.

This started with about 140 hours on the engine (2015 model but built in 2013). It happens when warmed up, especially when engine rpm is above 2000. Will re-start after a minute, and runs OK at low rpm. Mahindra dealer thought it was a fuel delivery problem. First they replaced the fuel filter. Still had the problem. Next they thought the fuel cap was not venting properly. While waiting for a new fuel cap, I tried running it with the original fuel cap loosened up several turns. same problem. Then I ran it with no fuel cap just to check it. It still did it. So, suction in the tank is not the answer. There is no evidence of antifreeze in the fuel or oil in the radiator, so I do not think it is a blown head gasket. Any ideas here? The dealer seems stumped.