This has been an issue for as long as I can remember. It’s extremely bad with world projected UVs; If the edges of a face line up right with the edge of a tile, you’ll get what looks like z-fighting. I posted about this in this thread 6 months ago, and encouraged another user to report it as a bug.
Unfortunately Epic’s bug reporting process ensures the community will have virtually no idea if this is a bug, if it will ever be fixed, or if they’re even aware of it.