Hi Guys again !
I wasted yesterday trying to fix this issue. Finally i did it!
I tried the all medicine described above. I updated UE for the latest official version, clear installed several versions of graphics card drivers(latest, May 2017, February 2017), played with forward rendering, etc - nothing helped. I have been dancing with tambourine around UE the whole day. Then, i remembered that i turned OF real time rendering in the editor viewport since i added dynamic sky into my project and my head started spinning. I turned it ON again and wow bingo it fixed it to me !
I realized that the issue is related on some subset of old Nvidia cards, i guess it was nothing to drivers but under special circumstances UE4 editor produce card’s wrong behavior. Despite of this - a game compiled in shipping configuration works great on the same PC.
I am a C++ guy so when i will have free time i will dig it deeper.
Cheers!