Any tiny spot not covered by a workbench area will allow spawn groups in.

You either have gaps in your coverage or mods have messed up your game files.

If you are sure you have enough workbenches and every spot is covered inside the walls and animal pens and gardens then I suggest you ...
Uninstall the game
manually go to the folder and delete the entire game folder
Reinstall game.

If you have badly corrupted files or out of date mod files and uninstall will not remove them. An uninstall only removes files the game thinks it put in. You must manually delete the folder after the uninstall.

Test game function.