So I was attempting to make an automatic melon farm. As you can see in the first picture, that is the device I designed. The only problem with it is that it only works when placed on certain coordinates. I'm not sure how the thing I made works but I had no clue why the thing only worked on certain coordinates, so I went into my creative world to test it out. My first test was at coordinates -273, 4, and -1095 to -1432. The results are kind of long and hard to explain so I won't address them here but if you want to see them I can follow up with them. Anyways, the coordinates on which I was able to make the contraption work made a weird pattern, and I was able to predict the next ones. The thing is though that the pattern changed every x amount of blocks and as you get farther away from Z=0 that amount of block increased by 3. So, since the problem seemed to have relation to the center of the world (0, Y, 0) I went there and tested it there.

The second picture shows that test graphically, I didn't finish it entirely (it was in a 41x41 area, that's like 1600+ blocks!) but I marked the results. The grass blocks are ones I did not test, the green (green clay) are where it didn't work and red (red clay) are where it did work. (side note: I figured out that, in my machine, it matters where you place the piston and not the other things in the machine. You can build it facing any direction and the result will be the same, so I marked the block that I placed the piston on.) As you can see it makes a weird pattern, I have no clue why though. I figured this had to do more with seed and deeper things than just the actual blocks so I decided to stop. If someone knows what is happening they probably won't need the entire thing. But yah, if you want to figure out why this is happening I would start by figuring out what my contraption is doing. I want to say its a bud switch type thing but I'm not sure. Then go on to figure out what that has to do with coordinates. Hope this gets fixed because I want an automatic melon farm lol!

Few more things, the diamond block in the middle is (0, 4, 0) and it was not able to make my machine work. The walls on the outside are at 21, so the inside should be 41x41 (including 0). I did not test how the pattern changes at different y values, so just to clarify again i put the piston on top of the blocks in the picture, then when i confirmed whether it worked or not I replaced the block I placed the piston on with the colored ones.