[IN PROGRESS] Glitch shadows: appear, disappear when its want

Some strange with Shadows in Unity 5.3.0f4.
Shadows works when it want.
Shadows works, and after few second gone. Or NOT. Like as lottery.

PS. 5.3.1 contain not stable?

Strange, strange. Now I try again and no this glitch… If I will get it again - I will send a screenshots.
Need reload Unity sometimes? :-/
Not stable version…