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.

in 1.1.3 maps will regenerate if the following conditions are met every 30 seconds:
-player is 128 blocks from map center
-map center does not fall within specified biome

this should assuage some of this issue but its only a band-aide. Will need to keep researching why sometimes the caves generate in wrong positions

Have you changed any config settings?

I haven't touched the configs, and I've run into this same problem where a magnetic caves map led me to a primordial cave. The actual magnetic cave is said to be about 6000 blocks away by /locate. The map seems to have all the other nearby biomes correct, just the wrong cave type.

My modlist is:
Alex's Caves, Alex's Mobs
Citadel
Corpse
Create
Curios API
Jade
JEI
Mouse Tweaks
Sophisticated Core, Backpacks, and Storage
Xaero's World Map and Minimap

same issue, primordial cave map bring me to magnetic cave (1.20.8)

Is there any intention to actually fix the problem or will @AlexModGuy just keep redirecting people to this issue? It's kind of a major problem with the mod. In my case, maps leading to forlorn hollows or abyssal chasm actually lead to regular biomes

in 1.1.3 maps will regenerate if the following conditions are met every 30 seconds: -player is 128 blocks from map center -map center does not fall within specified biome

this should assuage some of this issue but its only a band-aide. Will need to keep researching why sometimes the caves generate in wrong positions.

That explains what I came to report. I seemed to be in the area of the map, still digging to try and find the biome, All I was finding was Spider Cave. At one point I noticed that I was in the corner of my map. I thought I went too far and wound up off map.
Upon closer inspection I realized the map looked different.

Could you add a block counter that has 0 as the center of the current map?
So that when the map changes on me, I can see the distance to the next supposed location of the biome.