I am doing a simple wall, straights and 90 degree corners.  Using the same section for 90% of the work.  But my wall studs keep running into trouble.  This section i am working on should have 14 studs, all the same.  and it does draw them, but when i save the product i get 10 good studs, and 4 broken ones.

Now i did manually add 4 studs...but it wasnt these four.  Any idea what might be causing this?