Jonas Bruneau

Also, I realized that shipwrecks and underwater ruins generated in already explored terrains without any issues, so your statement about "structures almost never generating in already explored areas" doesn't seem to apply for all. Just thought I would mention it cause that's another thing that doesn't make sense to me.

By "now fixed", you mean post 1.13 ?

I will check if and how I can delete chunks, where we might have traveled but nothing of interest is located, as I currently have no idea how to do so. Same for the structures.

I didn't not know that, thanks for the info. However, how do you explain that I found a buried treasure chest near my raided ocean monument, that I spent 50 hours clearing out and 100s of hours afk'ing at (so the area was obviously explored), and that an area thousands of blocks away that I've never been to was missing its buried chest?

I will do more testing by teleporting myself 100 000 blocks away from spawn, and look for buried chests there to check that they are all generated properly. And if that turns out to be the issue, I will use a software to reset all areas of the overworld that have no player made construction and hopefully, the generation will take place properly.

Any other idea on how to fix this when migrating servers? Is it possible to reimport all player made builds onto a new server using the same seed for example?

Confirmed that this issue still happens in 1.13 released a few days ago. If any buried treasure map is found, then the buried treasure is located, looted and the chest destroyed then replaced by a solid block, any map in the vicinity found before or after (the after is important) will still lead to that buried treasure chest that you already looted. This goes completely against the mechanics of the game, as mentioned above where cartographer point you out to the nearest unexplored structure, and not the nearest structure no matter its current state. 

So my question is, what is the point of this? It makes maps and exploration completely useless as it is, with 10 maps having 10 different IDs leading to the same buried treasure chest you already looted. Here are a few screenshots showing 2 different buried treasure maps with different IDs, one looted before and one after, and all pointing to the same chests that is already looted: https://imgur.com/a/5ZVP2eo

I saw someone mentioning woodland mansions above. I had 2 woodland mansion maps on me at the same time in 1.12 that I got from cartographers, and they were leading to unique woodland mansions, as it is supposed to. Having 10 maps leading to the same place is just a waste of time for players and doesn't make you want to look for them.

I see a few ways of fixing this: apply the cartographer mechanic to buried treasure maps, making each map unique and leading to a different buried treasure chest, or make only one buried treasure map available per buried treasure chest area/vicinity. First one honestly sounds a lot easier to implement, as it is a mechanic already existing in the game and also the one that makes the most sense.