Cave map took me to the wrong biome!

[ghost]

I made a magnetic cave map, followed it for 9000 blocks and it turned out the biome it took me to was actually a primordial cave. Just to make sure there wasn't actually a magnetic cave somewhere nearby, I recreated the world with cheats, went to that primordial cave again, and used /locate to confirm that there actually wasn't a magnetic cave within several thousand blocks of there.