When placing stairs in a zig-zag/diagonal fashion, they seem to only connect properly and form a corner orientation if the order in which they are placed is the same.

To elaborate; if I zig-zag stairs from left to right, and then try to do the same from right to left, so that they meet in the middle, the two lines of stairs will not connect together, and so far as I can tell it is nearly impossible to make them (I tried placing in many different ways; against one stair, against the other, against the ceiling/floor, making the "middle" both an inner corner and outer corner, every way I could think of). After rebuilding a short line of stairs over and over again, every so often I could manage it, but as far as I can tell I can find no rhyme or reason why it happens sometimes and not others. The vast majority of the time, it fails. If I place all the stairs going left to right, or right to left, it happens flawlessly.

This happens even though there is no visual difference between the two lines of stairs; there is no way to tell if one line was placed left to right or right to left. There is no reason why they shouldn't connect.

Sometimes they seem more likely to connect if the stair at the beginning of each line is placed in such a way as to allow the second stair in the line to be placed as a corner stair immediately, without having to place a third stair in order to corner it, but this still doesn't always orientate properly until I break the whole line and rebuild it.

I've attached screenshots that hopefully illustrate the problem more clearly. I use a blackstone stair in the middle to more clearly show the issue. The fact that the middle stair is blackstone and not nether brick is not why this is happening, I've tested and this is the case even if the stairs are of the same type.

I have to redo an entire diagonal corridor now because I placed the stairs in the wrong order.