CM Group permissions working incorrectly

Hello experts, I am having a conflict with folder links permissions assigned to groups. I created a KM Navigation iView which has as entry point a certain folder. Inside this folder there are links to different folders (5 folders, actually), and we have the same number of groups who will have access to these folders. I gave each group read permission to its corresponding folder link. A couple of groups must see more than one folder link, so I gave them read permission to the additional links they should see. However, once any user opens the iView, he is able to see all folder links and access them freely, regardless of the group to which he belongs. I have checked the permissions many times and I cannot find the problem. I removed the group "Everyone" from the permissions of all links and folders, and instead added only the group or groups which should see each link and folder (for the links, I gave read permission, for the folders I gave read/write permission).

Any ideas?