Since I can’t post the images I had ready, or even links, I’ll just leave a note:
The Naga unit “Tidal Guardian” has a texture issue.
Not when viewed in the PTR map editor.
Not when entering the game through “Test Map” in the editor.
But ingame as entered through the PTR client — Custom Maps → Create → Start.
https://imgur.com/UOAGBJk
https://imgur.com/To1l1tF
https://imgur.com/SLpgKAH
Edit: The bug is in classic mode.
Edit2: Adding images through the forbidden knowledge of dark forum lords