I have a Nether portal very close to the world spawn point (that might be irrelevant). When I first made the portal, I had no issues with it, however, as of recently I started to hear the suffocation damage sound on the loading screen when entering the overworld only, and then I exited the Nether portal without taking damage, although occasionally there would be one more suffocation damage sound and I would lose half a heart. Since then it has gotten worse, and now I lose half a heart per sound while on the loading screen and, while it hasn't killed me yet, I have been taken down to one heart/one half-heart. The Nether portal has a considerable amount of clearance all around it. I do not believe it is correctly synced up to the corresponding location in the Nether, as I did not change its position and accepted the game's positioning of the portal. There is no other portal in my world that has this problem. There is no other portal connected to either of the portals. It was the first portal I made in this world. I am pretty sure that neither of the portals have been altered since I created them.