I have found that sometimes when opening an elytra that you will just be able to walk through blocks. It is only the top block though and there cant be any blocks on the lower half and with this the top half of your body can walk through anything but will still suffocate. Unfortunately this has caused me and some others to fall into the void by getting this glitch on the path to our enderman farm and they just ended up walking through the blocks.

I'm sry if this isnt enough detail hopefully this video of wut happened to me will show u wut the glitch is