Some textures not tiling despite identical import/material settings (UWP phone)

In my game I have 'wallpapers' made from a world-space shader that tiles different textures.

Everything is working fine except on Windows 10 Phone, where some textures don't tile correctly. On Android, UWP (PC), UWP (Xbox), Unity editor, all materials/textures behave as expected.

But I can find no differences between the textures and materials used on the wallpapers that work and those that don't.

Here are the import settings and materials for two materials, one of which tiles correctly and one which doesn't (the pink one tiles correctly):

http://imgur.com/qFil0hU

http://imgur.com/AYOjCHf

http://imgur.com/c0xoOhR

http://imgur.com/261BmOw


Both images are in the same format (.png, 200x200px, 32-bit colour), and were created in the same software (Snagit 13, FWIW). As you can see, the materials both use the same shader. Also, the two materials are used on instances of the same prefab, which is just a quad using one of the materials.

As far as I can tell, there is no difference between these two textures and materials, yet one works correctly and the other doesn't. Is there something else I'm missing?

 

I have solved this. The issue was that the textures were not 'power of two'. Resizing them to 256x256 fixes the problem (though it's odd that it only affected some textures even when others of the same size worked fine).

It does seem like poor GPU drivers might be the culprit.

Thanks