I placed trapdoors at eye level in front of a portal in the nether that was blocked from the other side. I opened one of them to enter the portal. Upon return from the overworld portal I wasn't able to leave the portal despite the trap door being open. I tried to open the other trap door. I was able to open it however when I tried to leave it wouldn't let me. I was able to destroy blocks around the portal but was only able to move within the portal frame and was unable to escape it. I could trigger a resetting event where I would fall through the portal and nether when I shot my foot with a arrow. This cleared the animation but didn't allow me to move.