AutoCAD Architecture walls have a justification line and a width. Sometimes snaps will only work on the justification line and not on the linework determined by the width setting. After some aggravation with this, I’ve found the cause and the solution.
ACA will not snap to both sides of a wall if layer “0” is turned off. Be sure to keep both “0” and “defpoints” turned on in model space and in all paper space viewports.
As a general rule neither of those layers should actually be used to show linework in a drawing because they have so many behind the scenes uses. Layer “0” is used so heavily in blocks that you really want to always have it on. The reason that I ran accross this dilemna this week was drawing an addition onto CAD drawings produced by someone else. They had made heavy use of layer “0” for linework and hatch.