Subassembly link missing at end of region

[Neilw_05]

In the attached screen capture you will see a longitudinal link is missing at the beginning of the corridor region. This is happening at the beginning of every region along this baseline. It does not happen on any of the other 3 lateral baselines. What causes this?

[Neilw_05]

I've stumbled on a solution though I can't explain what causes the behavior in the first place.

To fix it I created a gap between the 2 regions which caused the omitted link to appear. When I dragged the region grips back together the link disappeared again. The only way I could get it healed was by dragging the beginning of the problem region off the curve and onto a tangent, then closing the gap. After that I could drag the seam back onto the curve and the link stayed.

My workflow may be a factor. I first created the corridor with one baseline, region and the full ditch assembly. I then split the region at the baseline junctions and inserted new regions using the Fill option and applying a left or right ditch assembly. I suspect using the Fill option caused the behavior.