coolant burn-off

[hullothere]

Looking for information on a slight coolant leak on my 2015 GMC Duramax truck.   The truck runs great.  No warning lights.   Coolant tank looks a bit full, but otherwise have not found any wet spots or spots that look like a leak.  The dealer which I purchased the truck stated it was a bad reservoir cap and replaced it.   I noticed this when running the vehicle up to temp, it had previously started placing a coolant smell into the cab, and a slight white smoke came in.   It took them a couple of days to find the issue.   They changed the cap, then all ran good for 5k miles.  I began smelling it again.  Figure the smoke will come back soon.  Could this be a symptom of something greater?   When the vehicle smoked, it came through the air system on the truck and under the hood on the passenger side.