Mineshafts sometimes generates underwater and it would be fine if they wasn't filled with air.

Please provide mod list as well as world seed and coordinates where this happens

Sadly, I can't as I deleted this server and created new one with Fabric.

But I remember few details if this can help. The only mod which changes World Generation was Biomes'o'Plenty and the biome was Warm Ocean. Generated shaft was very short and single one.

Hey, I noticed the same problem. It happened with and without BOP. With BOP installed I saw it more often but thats just a feeling. Also I think with BOP installed the mineshafts are sticking out more. I didnt test it on 1.16.2 or 3 - still waiting for some other mods in my modpack to update :)

Mc: 1.16.1
Forge: 32.0.108
Better Mineshafts: 1.16.1-1.3
Seed: test
Coords: x:790/z:190
with BOP installed on same seed at: x-170/z:70

This should be fixed for 1.12.2 as well as the 1.16.2/3 versions. The fix won't be coming to 1.16.1.

Awesome thank you!