Your results will not vary. I frequently encounter these abrupt discontinuities in the noise-based textures. There is some error in the implementation. I have usually had to offset the pattern or combine it with another copy to hide the artifact.

Please help figure this out as it drives me nuts often - I'm vacationing and can't do it at the moment.

Try different scales. Try using constants in the other two scales (an add node with a fixed number). Try using the V coordinate for Y_Scale.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)