Small conveyor tubes appear to have larger collision or other factor than a vanilla tube. This is causing many blueprints having tubes buried inside small ship structures to fail to be weldable. This is really odd. I'm able to use the 6-way conveyors in their place, while functional, it does look a bit naff, heh.

If i remove the mod, blueprint immediately returns to be fully weldable. Which is what makes me suspect the tube itself.