Lack of precision in ceiling plane placement. How is this supposed to work?

[GeneDavis]

I've a 4:12 ceiling plane defining the scissors truss envelope.  I draw the ceiling plane baseline right at the wall framing line, not at the drywall face 1/2" inboard, and set the height of the baseline at 109 1/8" to match plate height.

 

But it does not place the plane correctly.  It is lowered just about exactly one-third of a sixteenth inch.  See the pics.

 

What is this behavior all about?  I tried raising the ceiling plane using the move tool, inputting +1/48" in the z axis for the move.  It did not move.  I deleted the planes and redrew them, specifying wall height at 109.125, and still got the error in placement.  I drew a new test plan and did not get this error.

 

The CAD boxes you see in the closeup are rectangles to measure height.  The large rectangle is 1/16" high.  The three small ones, are each as high as the error, and it seems weird that they are exactly one third of a sixteenth.  I stacked three to see.

 

If you want to download the plan, look for the thread I titled how to delete these ceiling lines in my elevation view, in this forum.

Edited Saturday at 07:09 PM by GeneDavis

[robdyck]

There's a couple of things that could be adjusted, but this is project has a buggy ceiling plane. It is not building as it is spec'd and I'd report this as a bug.

 

In this plan, here's what I see for the ceiling plan (top of screen). the Hieght Inside Wall is not correct.

 

Ceiling plane at bottom of screen is in the wrong location, but it's height is correct.

[robdyck]

It does build correctly if you just replace the goofy ceiling plane. That thing seems to be hardwired to be troublesome.