I do not know the control system, but I have a few ideas:
Status (LON) on SMLCD (top row, 1st and 2nd digit from the right).
It is possible to give an landing call up and down individually from the servicemenu?
How many floors does the elevator have >3 floors?
if you have more than 3 floors:
Change the address of floor 2 (HPB S4: 2->3) and of floor 3 (HPB S4:3->2).
Is the problem still at floor 2?
the microswitch on PCB is mechanically actuated when the button is pressed, press the microswitch directly ->?
disconnect X4, X1 -> ?
Is the problem now at floor 3?