Select the walls around your 1m2 staircase
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Select the rotation of your 1m2 staircase

There is a wall at the left of your 1m2 staircase. You might want to change the rotation to anti clockwise to improve the walkability.

There is a wall at the right of your 1m2 staircase. You might want to change the rotation to clockwise to improve the walkability.