This may be the effect of Strutural Snaps. These are used by Structural elements to intelligently join them, look up "Structural Snaps" in the help documentation for more details.
If your columns were both placed by a corner and Structural Snaps are On the wall between them will snap to the Column placement points. In this example the column was placed by centre so the wall snaps to that centre placement point:
Note the Structural Snap icon that pops up.
Structural snaps can be toggled from the menu: Building Designer > Structural > Structural Snaps.
There is also a Structural Snaps Toolbox: Ctrl + T to open the Toolboxes dialog > Structural Snaps.