By default mobile uses half precision in pixel shader calculations to improve performance. You an either perform the texture coordinate math using full precision by checking the "Use Full Precision" checkbox in the material (under Mobile), or by using a Customized UVs to perform the UV math in the vertex shader, which always uses full precision, and passing the result to the pixel shader.
There's an extra nuance for external (media) textures which can make them use half precision even when using Customized UVs. If you notice this, use the Full Precision checkbox.
Offsetting UVs can result in blurred texture on Android/Quest
Confirmation in MAIN 4.25 @ CL 11384989 blocked by [Link Removed]
Result: The texture that has been multiplied and added will be blurred. (no blurring on pc)
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-88736 in the post.