Solved !!!! With thanks to those that helped me narrow this down.
OK, curiously, although I had my GPU selected for use with CA, somehow that was changed to allow the integrated processor to handle CA. No idea how that happened, but simply pointed the processor back at the CA X7 and back in business.
I post this to help others that may find they have this type problem. Don't assume that what you did can not somehow get "undid". I never checked the very simple solution and assumed my GPU was still handling this, but in fact it was the integrated Intel processor that was evidently the problem. Now I wonder why the Intel is having a problem, but not as concerned as this really was the only manifestation I have seen.
Lesson to me? Don't assume and don't ignore the obvious. Thanks again guys !!!
I write this to hopefully help others, who might experience same issue, and not as a knock in anyway to you. I did this early on in my CA learning curve to a much lesser extent.
As it looked like z-fighting to me, I have learned that this can be caused by generally just four things..
1) Two objects in same space. (checked this and not your case).
2) Too thin a material. (can't really be the case here, with objects that were fighting, but you will see this on roof tiles and siding sometimes. If you do, simply change the material thickness to like 1/4" or something and it will fix usually)
3) Too large a terrain perimeter (not bad in your case)
4) Too far from origin. Bingo, we have a winner. See below shots, but in the all on (lower floor) you have some type of site plan a few MILES east (to the right) from the actual house and terrain perimeter, but that was not the really issue. The real issue was that you were, holy cow...... 10.5 MILES, yes miles, from the origin. That's way out of the range of this program, even if the plan was to build a subdivision. (see photos attached)
Lessons here. Start your plans at the origin. Tommy Blair taught me years ago to set a few walls in an "L" arrangement, about 6 feet long is fine, right at the origin (0,0). Now save as your template plan and you will always start right there, as walls are usually the first thing we do.
Although it is not unusual for AutoCAD folks to have things all over the space, does not work here. The site plan way out to the east, need not be there. Should be a layer. If you are first floor, all on plan, click the zoom extents to see what might be hidden out there. If anything is outside your terrain perimeter, find and get rid of it.
Oly (and please add your name to your signature, with version you are using) here' how to fix your issue.
Once above is done, Click Edit > Edit Area > Edit Area All Floors. Draw a marquee around entire plan with perimeter.
Next Click Transform Replicate Tool
Make Sure Absolute Location Radio is selected
Make X and Y (0, 0)
This can be messy at times, so save a copy before you start.
See photo attached. The tiny little black dot top left is the entire contents inside the perimeter. The "X" is the origin 10.5 miles away. The other blur to right of the plan perimeter is a site plan or something (can't be there)
Wow !! Nice Michael. I was trying what you said and you already had it.
So I understand this, and perhaps for others to learn go forward, is there a "proper way" to place a shed on a dock (deck) to avoid this kind of issue? Is it that I need to avoid crossing the edge of the deck with any part of the shed? Or if so, create breaks first? Not sure still I know the answer, but you definitely solved the problem. For now, I need to avoid all structures on the deck or make a copy to experiment with first.