Hey sorry for the late reply, i didn’t see the notification until now.
You can enable ‘Relative Tiling’ on any of the materials and it will keep them world aligned as long as they’re on a horizontal surface - This way when you move/resize an object with the materialo n it you can peices multiple objects together and the materials will always line up.
As for the Tessellated Landscape Materials they can be sensitive so you have to make sure to be careful how you utilize them. I would recommend making the resolution of your landscape actor a bit higher if you scale it up and try to keep it as close to the resolution of the Landscape Actors in the demo as possible for the best results but you can lower it a bit without much loss in quality.
If you want to post a screenshot of what yours looks like i can get a better idea of what may be causing the issue.