Slanted Wall Joins in Revit 2021

Following on from my Analysis of Slanted Walls in Revit 2021, and Analysis of Slanted Walls and Rooms in Revit 2021 let us see how it handles slanted wall joins in plan.

Mysterious Behaviour

I have not yet figured out the rule for this, but it seems that slanted walls sometimes join properly in plan and sometimes not . . .

The failure of wall layers to join seems to occur at varying wall angles and different view range cut heights.

At gently slanting angles the problem does not manifest itself:

• At 25 degrees (or less) with a standard wall cut height of 1200mm (or 4 ft for the imperialists), the wall joins ok
  

• Bump the slant angle up to 30 degrees and it fails
• In this example the base offset of the wall is raised 900mm above the Level that it is hosted on - that causes all kinds of issues, but it is not the problem here

• Change the 'View Cut Plane Height' to 1000mm, and it works again - but of course the cut location of the wall changes

• Change the angle to 45 degrees and it breaks again
• It seems that the base height of the wall has no influence on this (providing it is below the cut height).
  

There must be some mysterious formula that combines the cut plane height with the wall slant angle that makes it work or fail!

Of course it should not fail at all - why doesn't it just work as expected?

Talking of "Course", this problem doesn't show up in Coarse views - only Fine and Medium detail levels.