Problem: Build (not PIE) has one of the nearby textures running through the landscape following a grid, as shown in these images.
They are not in the Editor:
I use a Landscape Layer Blend with auto materials passed in, so I can paint the different biomes.
I use RVTs but only to color the foliage, which isn’t drawn more than 10,000 units away. Otherwise, the RVTs are disabled for the landscape texture.
I use Triplanar, only on the materials that are steep, such as the cliffsides and a canyon wall (not shown in these images). Although, most of the lines appear to be on the cliff, they are across the entire map. I disabled Triplanar on every Material and the lines are in the same places.
Every Texture uses Sampler Source → Shared: Wrap, and MipValueMode → None. I have tried changing those to each other option, with the aforementioned selection giving me the best result.
Finally, I have my caps lock off (I swear I’m not hold shift) and I’ve turned it off and back on again.