I am struggling with all of this myself.
Because you have edited at least one of the stair nodes (the yellow warning triangle next to nodes warns you there are custom nodes), the stair no longer seems to work as one complete unit.
Adjust the railing end in the stair settings and it may not apply to both ends - the other end may well be adjusting.
You can 'Reset' the custom nodes by pressing the reset button at the bottom of the settings dialogue - but this will reset any custom edits.
However select your stair and go into the EDIT mode.
Now select the top rail and hover over the end node.
TAB to 'toprail end' and then click to select it.
Now you should be able to edit the end values.
Once you have an end on the rail they are easier to select by using quick select mode (magnet) to select the surface.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11