Here's what I've been told by a good Archicad guru felllow.
If the tread edges at the landing tread where the stair treads and risers are overlap then the stairs will get freaked out and can't seem to calculate nor create the stair properly.......yet in real life, stairs have offset tread edges ALL THE TIME, yet for some reason the formula associated with creating these treads and risers goes haywire......such a shame.
see attached explanation in 3D.
...Bobby Hollywood live from...
i>u
Edgewater, FL!
SOFTWARE VERSION:
Archicad 22, Archicad 23
Windows7 -OS, MAC Maverick OS