Without the plan (and almost none of us have X7 installed) there's no way to know what you are doing wrong.
That said, try the following:
Draw a railing wall in the basement next to the stairs.
Move that railing wall so that it's main layer is on the stair.
Set the railing wall to "Follow Stair".
That should work. If not, post the plan and maybe someone can do it for you.
BTW, why have you not upgraded since X7?
X11 has much more capability.