Khitan stair corner not working properly

Game mode: [Online | PVP Official server 1808]
Problem: Bug
Region: [North America]

When upgrading an entire stair set I built out of Sandstone to Khitan, all of the normal stair pieces upgraded perfectly fine, but when I got to upgrading the corner stairs, everything from the corner all the way down broke off and will not replace.

Steps on how to reproduce issue:

  1. Build corner stairs out of sandstone
  2. Upgrade existing T! corner piece with a Khitan piece
  3. Corner being upgraded and all pieces below it will crumble and leave a big gap.