Background Causing Invisible Blocks?

There seems to be a bug where when I place blocks in the background, it creates invisible blocks in the game world. Getting rid of the background fixes the issue. The block doesn’t show up in any layer, but is in the way during gameplay.
Game is here
Update: What’s even weirder is that it sometimes goes away. It may not work when you enter.
Another Update: The glitch stopped for some reason, but it has happened on other occasions.
Ok, Last Update: The glitch happened again…

This always happens to me

I think it stops happening once you exit and re-enter the game. Glad to know I’m not crazy