Near\far clip works differently at PC and Android

Unity 5.6, there are 4 cameras rendering 1 terrain + some mesh objects, to 4 render textures Then 4 render textures are applied to 4 quads, so terrain rendererd only once at some changes

But only at mobile same corner (4th render texture) rendered with this artefact which looks like depth issue (river) and black spots at fields (???)

Bug apperas only when there are a lot of stuff at this corner (a lot of fields and buildings) if remove some fields and building - all rendered ok.

All 4 cameras and render textures have same settings, it is not mip maps. Culling is turned off at cameras.

Any ideas? is this corner is 'too heavy' and camera can't handle all objects?

Looks like it some kind of culling issue, I've moved quads aside, and now there are more black spots..