Shulkers are spawning in overworld

Hello,

I've recently encountered a bug in Minecraft 1.16 in singleplayer mode. Shulkers are spawning in my world. I don't know where it can come from. I've quickly saw that commands in the game are not working like /seed.

I let you a Youtube video link here: https://www.youtube.com/watch?v=FwHu83KwmU4

I attach a screenshot if you want.

I give you THE world I used (37.28 MB): https://www.mediafire.com/file/pazq13wnr753lo5/Monde_en_1_16.rar/file

I don't use any datapacks, any mods, any command block or other.

 

I have also trying to re-create the same world and there are no shulkers spawning.