https://gyazo.com/73c758f29a1e1bd585e894d0efb3a1f6

Interesting, but as far as I know it works, if this happens maybe another mod is hooking into the render of the falling blocks, let me check this.

After testing I was not able to reproduce this with any of our sands nor menelaus sand/gravel.

I guess this is ahepening because of sponge, as I was unable to rpedroduce this in single player & on our forge server.