Thanks, seems to be working fine

The error is on line 441:

return createUShapedStaircaseShapes(stairCount, firstStairCount, 1, turnStairCount, stairWidth, stairDepth, stairHeight, treadOffset, treadThickness, true, riserThickness,
should be
return createUShapedStaircaseShapes(stairCount, firstStairCount, turnStairCount ...

Hi Xlance,
v4.0 looks really great and I love the more detailed options!
However, one flaw that I found is that when you select "U shaped", the generator will create a "U shaped with bottom landing instead" so something seems to be linked incorrectly there.

Thanks for the nice work!