Overworld mobs spawn in the end on cobblestone

In our server, I had branched out 128 blocks off of the edge of the main island of The End dimension and had made a cobblestone platform, and as I went more than 22 blocks away and came back, I saw zombies, creepers, skeletons, spiders and bats spawn, and no endermen. Upon some research, I found that this is a bug that happens when upgrading a server to 1.18, that the game takes it as if bit far from the island there's a plains biome, and this still occurs in 1.18.1. Please fix this as fast as possible.
Thank you