World Composition -- Gap in Landscape Splat Material

When I import a set of tiles from World Machine (505x505), I am seeing a gap in the Landscape Material (image 1). I’m using a Splat Map. This gap is also visible from the WC Window (image 2).

In image 1, the thin white line along the gap is actually the top row of pixels in the splat map. I changed their color for debugging.

This occurs regardless of scale (100/100/30 and 500/500/150), regardless of the WM Export ‘Participate’ button, and regardless of the +1 “Size” checkbox in WM.

When the material is updating, it looks like there is an extra row of quads in the default checkerboard material.

Please Note: I am not referring to the landscape gap. That is easily fixed with the smoothing tool. The issue is a gap in the material. Image 1 also includes the landscape/mesh gap for reference.

Comment: As I was posting this question, I went back to try another approach. That new approach improved the situation and reduced the issue, but did not fix it.

Thinking that maybe, I could add an offset to the splat map, I checked the Landscape Coordinates node. The Coordinate Mapping Scale was set to 505, to match the World Machine import.

Looking through the details of my Landscape, Gizmo, and Streaming Proxies, I found a setting (can’t find it now) for X and Y Landscape Scales. X was set to auto and Y was set to 504 – one less than the 505 tile size. These settings were not editable.

Setting the Landscape Coordinates Mapping Scale to 504 greatly reduces the material gap, but the issue is not fully resolved.