Mask+runtime generated texture2D bug

Hello everyone. In my project I have a texture2D that is generated in runtime, and a preloaded texture2D, both under a mask. When I try to increase their scale and move them with scroll rect under this mask, it behaves strange on some devices. The result is on the screenshot:


And here is what I need and how it is in devices, that work fine:

Who can tell me why is that so and can I fix it?

Is it a unity bug? Maybe I should make a ticket to a bugtracker or smth?