Error Message When Editing Profile of Wall

[colinX7B66]

I'm trying to create a switchback staircase like the following image shows:

However, when I try to edit the profile of the wall, the wall will not align next to this one riser as shown here:

Here's an image of the issue in the 3D, if that makes it clearer:

Have any ideas of how to fix this issue? Or maybe I'm taking the wrong approach to creating these stairs. Thanks for any help.

[ToanDN · Accepted solution]

Disjoin that wall from the perpendicular wall under the stair. In other words, select the perpendicular wall under the stair, right click the end point and Disallow join.

[colinX7B66]

Thanks! That worked.