Damaged while flying near nether roof

Hello, I play Minecraft on the Switch and recently in one of my survival worlds I ran into this issue: I find that it is fast to travel in 3 high by 2 wide tunnels with elytra and fireworks. Now, while setting up my network in the Nether to do this, I decided to set it up close to the ceiling so that I wouldn't have to build bridges and mostly just dig out my tunnels. I left 1 block of netherrack between the tunnel and the first bedrock ceiling blocks and built it (Therefore I do not see any bedrock and the tunnel walls are only made of netherrack). However when flying in my tunnel I begin to take damage while gliding along the roof or walls of it. This does not happen at lower altitudes in the Nether nor when I have tried it in the overworld. Please help solve this issue as I do not believe I should have to build my tunnels at lower heights.