Mark3D

Select and open the wall, change its assigned layer.

Try and share your plan as this might be easier to trouble shoot with the plan to look at

It should work post your plan

If i understand you turn off auto roof return

Try to just import the major contours and not the minor contours you still might need some minor contours just copy the needed minor from another plan file, if needed to get correct shape. As to much height data slow chief down.

You might need to use the tab key to select objects below

I am not sure what you want, i think you need the top of the walls to be flat in camera view maybe try the cross section slider tool from a camera view 3d menu - camera view options

You have selected no ceiling over gym and the 2 living areas, as the wall surface are extended to under side of rafters and you probably need to adjust the heel height roof dialog its set to 8" maybe try 6 or what it should be to suit your local conditions

I had a go at it but no luck with auto matic tools, but chief has some manual tools to help https://www.chiefarchitect.com/videos/watch/306/using-the-trim-and-extend-commands.html https://www.chiefarchitect.com/videos/watch/337/mitering-framing.html those tools should working on the decking boards if there is not a better solution from others

If you delete it then the frieze molding auto forms

I would send this into support as you getting problems with this file one they might be able to spot the problem and it might just by tied to a bug in x18

If I delete the curve part of the roof the problems goes away, as a fix could the curved portion be done with a molding polyline you would be missing ridge capping so may not be suitable, hopefully others will have a better solution

See if that is this heading in the right direction its still a bit rough and need some fixing but no point if its not what you want. You had a heap of floor platform holes that was giving chief trouble that needed to be deleted and few other little problems 515040722_silobarnhouse mark edit.plan

You could try exterior room molding polyline

Have you looked at the new feature in x18