There is something not right with your ARCHICAD version.
In the INT version, Monolithic Flights have a 4th Connection Type, which would provide the necessary settings to solve this connection type. See the attached image.
Also, there is some glitches in the interface, those gray circles should be overlapping parts of the Stair Section, not be to the left of them.
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2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27