Still happening in 20w07a.
You can quit the game, and change fullscreen setting in the options.txt file located in your .minecraft folder to false (type run into your windows search bar, type %appdata% into the popup, locate .minecraft, and find options.txt in there, usually twards the bottom for me.) Then relaunch Minecraft and you should be fine.
This does not have to be a wall, but happens to trapdoors/fencegates anywhere, on any rotation as far as I can tell.
Not sure about 15w31b but it's not happening to me in 15w31c
Confirmed in 1.9 snapshot 15w31c
Confirmed for 15w31c too
Sorry my search settings were wrong 😛
I've been having this issue too since 1.16.xxx (sorry don't remember the exact version number but new world created in 1.16)
To add more info to the issue: Originally I had a end city portal going to the outer islands which worked fine both ways for awhile. Eventually the portal on the outer island started to move it's exit spot on the main island, slowly moving towards the center main portal to the overworld. After so many trips back and forth, it would shift a couple of blocks closer to the center.
I believe this started to happen when I started to build under the portal on the main island (was replacing the end stone with end stone bricks if it matters). Going out to the outer island was still functioning correctly. As I kept building to compensate for the new exit point (I was transporting items through the portal for storage on the main island) the exit point would move closer to the center.
This happened about 6 times and the final exit point was about 15 blocks closer to the center than when I first went through. Then at one point the main island portal shifted so instead of sending me to the island, it now drops me off a couple of blocks off the main overworld portal. If I place a block at the exit point, unload the area and then reload, the exit point will shift to a new spot around the overworld portal however, it will remain consistent (x,z coords) regardless of placing blocks IF I keep the area (including the end city portal) loaded.