Sometimes, when I try to cleave out stairs, the surfaces of the stairs will not show up in the 3d preview. And when I would cleave the unseen surfaces, they also would sometimes appear, and sometimes just remain invisible in the 3d preview. This sometimes also happens to me when I cleave out walls, or a floor. Could someone please tell me what is going on? How do I fix this?

It might be because the 3d preview doesn't always update properly if you do some cleaving. After a major cleaving job it's best to close the preview and open it again, or you can toggle the preview fully lit on and off to refresh the display.

I can think of 2 possibilities:

1) Look in the consistency checker (F10 in Jed). It might be that there are more than 24 vertices on the surfaces along the sides of the stairs. You can fix that by just cleaving the surface in half.

2) Close the 3d preview and start it up again. Especially if you use pluggins like staircrazy or get bent you will need to reset the 3d preview to see the new sectors properly.

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