Several things are happening with this model. First it’s hard to be working on an architectural scale with .000 mm accuracy, Sketchups internal tolerance is about 0.025 mm. You can adjust the precision in Window>model info> units.
If you look closely at the intersections none of these steps line up “perfectly”. These individual stair units are all slightly different sizes. Although they are a component, they have all been individually scaled and skewed from outside their bounding boxes, which means these size changes are not shared between instances of the component. You can right click on any one and select reset skew and reset scale to return each to it’s un-adjusted state. If you want to make scale changes that will be reflected in every instance, you must open the component for editing and select all, then run scale.
Was this spiral stair downloaded from the web? I guess that because the individual adjustments to each stair seem to me to have ben an effort to make things fit together roughly.
Because the stairs spiral inward if every step is the same size the outside edge will continually march inward and not line up every time, this is just how the step is drawn, not quite right. In an effort to overcome this it looks like someone has individually adjusted every step after placement to make it fit.
The solution would be to start over with the first step un adjusted, make your first copy/rotate with step 2 and check the fit. You may need to edit the component to make that initial relationship fit. Then continue with the rest of the steps once component is made to fit correctly.