found a previous post you shared. reading through the comments, and someone indicated that the sequence of selecting mattered. I found that I had to redraw the wall again, re-break and then select in the order you indicated. Hope that might help the next person. Thanks!
halversonjl's post in ANGLED STAIR WALL. I assume I will need to break the wall where it transitions to the angled wall, but unsure how to get the 1/2 wall to follow the angle of the stairs? was marked as the answer