Weird G-sync issues

Hey!
There were always problems with WoW and G-sync for me, usually I had to reinstall GPU drivers, or whole Windows to get it working or just wait for new WoW patch. G-sync was working for me like charm until 8.1.5. hit, now its suttering every 5 secs. Again, I tried reinstalling GPU drivers, then whole Windows, still stutter. I decided to wait again for new patch…
Randomly I found out while connecting external monitor (and WoW still running on laptop display, cause external monitor doesn’t support G-sync) and launching WoW, the stutter went away and its buttery smooth, g-sync sweet working. Wierd thing is after I disconnect monitor it still works fine, until I restart WoW, then stutter starts again. It only happens with WoW, any other game always worked fine with G-sync, even without external monitor. Do you have any idea what the problem might be? My laptop is Alienware 15r3 with 1070.
Thank you very much!