See screenshot, I used /locatebiome a few blocks from the present coordinates and got a biome at 324 ~ neg220, but then I moved a few blocks and the /locatebiome didn't pick up the biome at all when it should have.

Default world gen, no special settings. Latest 1.18 snapshot 21w40a.

I've also had it where moving just a few blocks locates another of the same biome but hundreds of blocks more distant.