Hi All,
I’ve been scratching my head for a while on this problem, browsed through loads of forum post and YT videos but found no solution, though this seems to be a somewhat widespread issue unfortunately.
The title pretty much describes the gist of the problem: artifacts/gaps between spline meshes.
What’s make things worse: it wasn’t present in UE4, I never had this issue back in the past.
So I made a really basic spline blueprint to create roads, really common stuff.
This is the UE4.27 blueprint.
And this is the UE5.6:
No surprises here, almost the bare minimum, using the Basic Plane mesh and a Grey material from the Engine Resources.
The UE4.27 works as expected and provides a nice, continuous mesh - for the sake of fairness, it shows gaps in the projected shadow but I don’t really care that much, it will be a road.
However, the UE5 version is different - and dare to say: not really usable in this state. 
Those dots between the segments are clearly visible.
Sadly, it’s the same with PCG:
I’ve tried many things…
- using solid meshes instead of simple planes
- turning Nanite on/off, adjusting its settings (Fallback Target, Relative Errors)
- turning Lumen/lights on/off, messing around with the settings (but Unlit mode shows the same issue in UE5)
- trying different things in the blueprint (get Loc/Tangents by distance, clamping the tangents, different splint point types,…)
One solution came up though: merge the BP actor to get a single static mesh but many times it isn’t practical.
I’m almost at my wits end because seemingly there are no solution or answer to this problem despite it looks a showstopper on many fronts.
)