**REPORTED** When the monster spits sand, it messes with the platform stair

[Marcos Moutta]

Steam or GOG

Steam

Single Player/Multiplayer

Single

Operating System

Windows 7

Terraria Version

1.4.0.5

Controls Used

Keyboard/Mouse

When the sand block touches the stairs, it creates this funny glitch, a piece of platform disappears!

 

[Sigma90]

Thanks for the report!
There's a known issue involving dirt/sand projectiles messing up stairs like in your screenshot. Fortunately it's a visual glitch only; there's no lost platforms or world corruption.