I have a heavily modded game, so that may be my issue. But when I create a door entity, place it, and try to open it, the game either crashes or the door clips out and completely disappears, leaving behind a big floating blue line in the world. Occasionally when it crashes, I get this error:

The game crashed whilst keypressed event handler
Error: java.lang.NullPointerException: Cannot invoke "team.creative.creativecore.common.gui.IGuiParent.closeTopLayer()" because the return value of "team.creative.creativecore.common.gui.GuiParent.getParent()" is null

I've updated Embeddium to the latest version. Sometimes when I open the door it pushes me far back and there's some blocks stuck on the screen.

It looks like the most recent updates fixed it! I occasionally get knocked back by the door but it doesn't glitch out like before.

Can you try out the newest version of CreativeCore and LittleTiles and see if this issue still occurs? Also please provide the entire crash-report otherwise it is very difficult for me to debug it.