Display problems with lightmap (High-End Mobile/Android preview)

Hi every one. I have some trouble when i use “High-End Mobile / Android preview”. I have some artefacts - Gradient noise. And when i use “Shaders model 5” all is okay.
When i change settings on “High parameters” (in Lightmass and Building light), it not help.
I could not find information about this problem.
Tell me any idea, if is it possible to fix it.
Thanks.