And here is my material, with the custom uv’s applied (I can’t use custom UV channel 1 because that is being used for the second uv channel that the object has)
Why don’t you use the UV0 channel of the custom UV’s?
Now the reason it is pixelated is because of Unreal using lower precision on mobile by default. Meaning it is not recommended to use high values as a UV input since it will look broken. So my guess is this pixelated effect comes from the fact you are using a Time node in the UV’s, which is for low precision fairly high after a couple of seconds. You could use a Frac before hooking your Multiply(Time, Speed) up with your Time input of the panner node.
I do not have much experience or knowledge about mobile rendering, but my best guess would be that you are somehow running into issue with interpolators to handle two custom UVs and reflection vector at the same time. Try removing reflection vector from your material, to see if it helps.
At the same time, try to changing material blend mode to opaque.
Please post the material or toggle the material stats on and off and post the errors. If you give me the material I can test it on my mobile devices. My guess is maybe mobile does not support that amount of custom uv’s.
I tested your material on a Samsung Galaxy S7 and an iPad3, both are working fine. Make sure all your texture samplers have an input texture assigned and maybe throw out your Binaries, Build, Intermediate and Saved folders from your project folder, just to make sure it recreates all your shaders.