So awhile back I made a video about the first 2 way under over door, and it's done well. However there have been a number of comments saying that it doesn't work anymore, and after some testing I believe that it's a bug. The reason is that the circuit is not working anymore is due to slime block unreliability. The problem being that the way the circuit works, slime blocks launch you into the next one, or that's how it's supposed to work anyways. Now it just pushes you forward one block and stops for the horizontal slime blocks, the vertical ones are even more unreliable. Somehow after testing I realized that if you have just a sticky piston facing upward with a slime block on top it launches you upwards normally, however with the circuitry somehow now it only pushes you upwards one block. I have no clue what's causing it, however I'm pretty sure it's a bug. If you want evidence, that's pretty hard to give, so I'd recommend finding the video for "first ever 2 way under over door" and the first result. If you try to build it and use it you'll see what the problem is. One quick way to see the bug though is to have a horizontal sticky piston and slime block setup with a single block below it, the only way for you to get launched is by shoving yourself up against the slime block, otherwise you only get pushed forward a single block.