If a cobblestone stair (/oak stair in every case in this text ) gets placed down somehow not by you (with setblock or by another player)
than you will not be eable to see it and if you walk againt it you will bug in the block^^ ;/

But the problem only appears when using cobblestone stairs with all the others it works perfectly fine!

(When pressing F3 + A or rejoining the server it does not update so there are still invisible!)
After resarting the server oak_stairs and stone_stairs dissapeared completly (on the last screenshot there has been a row of all kinds of stairs next to each other) now there is only air left at these blocks...