Hello Ron! Glad things are mostly working out so far!
Yeah, LayOut will snap to every little edge/endpoint in SketchUp. So if you have a bunch of small fragmented lines you could have some trouble. You might go in to SketchUp and try cleaning up the bottom of your walls.
Another troubleshooting exercise. Make a copy of the drawing you had trouble dimensioning. Right-click on it and ungroup. Then pull each of the stacked viewports apart and see if you can isolate the problem to a viewport. Then go look at that viewport scene in SketchUp.
Let me know if this gets you closer. Feel free to shoot the LayOut doc over to me, just make sure to update the .skp reference and save before sending. [email protected].