Relogging on top of slabs pushes player off of slabs

Was in the nether and logged off on the top of our nether hub. When I logged back in, I was in the lava below. I found a way to reproduce it, by rebuilding the shape of the nether hub tunnels and logging off on top of them. Strangely, when I wasn't above lava/ in the nether, it teleported me inside the tunnel. I am attaching a world that has the structure, one in the nether and one in the overworld.

Steps to reproduce:

1. Fly on top of structure
2. Relog