Bill

My hierarchy of considerations when I work through this type of drawing:

• Colour map-fg scrap - ensures you can see scrap edges while you are working (not relevant to your current example, but if helpful when the project gets bigger)
• Make sure yellow ticks point into the cave void ie -reverse status (not usually ‘necessary’ for pdf outputs, but affects kml significantly, and I suspect sometimes affects scrap joins)
• Only create non-visible walls in open scrap ends if necessary, based on trial and error.  Usually, they are necessary where the open end of a scrap is wider that the scrap is long. 
• Think carefully about -outline status and the type of line it is attached to.  Kml are particularly sensitive, and a good tool for checking this and all the above points.
• Only explicitly join scraps and lines if absolutely necessary ie based on trial and error (your example shows that some form of join is necessary in this case).  Start with simplest join approach and progressively try more constrained approaches (no count option, -count 1, -count 2).  Manual or point by point joins are a last resort, and should not be required for what appear to be simple open ends of scraps.

My experience is that while it pays to be aware of Therion considerations when surveying, pretty much any in-cave survey centreline misdemeanour can be accommodated when drawing scraps.  Some are easier, some are harder and experience helps.   Usually an apparently intractable problem can be traced to an errant object or property that you haven’t noticed.

This wiki entry might be helpful

https://therion.speleo.sk/wiki/faq?s[]=distortion#how_do_i_use_debug_mode_in_layout_visualising_drawing_errors_and_distortion

layout LayoutDistortion listed therein can help pin down the cause of unexpected problems.

Good luck

Bruce