Vamie

So i created a pocket dimension, out of curiosity i placed down a transdimensional trapdoor just in case so i wouldn't get lost in the dimensions below etc. So I open the trapdoor and try to fall through it, jump through it, i even went underneath the trapdoor and every single time i touched it, it closed on me automatically. What is happening? How is this fixed? I am really frustrated as I was so excited to explore the dimensions of minecraft.