If your vetices are slightly off grid, when you draw your line it may be snapping to horizontal/vertical line, thus not actually snapping to your other vertice.
Drag select the vertices, snap to grid then weld together
When it works its wonderfull, standard mod across all servers not different versions. Able to update your map and know everyone is playing the same version. Everyone having high speed download of the content without taxing the server/server hosts.
Been using it, its nice 2 quickly see the set things are coming from. I definitely see the need for the white, really exposes more of the prop in the image. Having said that, i kinda like to turn what i can to be darker, like the newer photoshop 3ds…