I have a list with many items and am trying to break inheritance on each item so that a user can only see what they have permission to. I broke inheritance on an item and assigned a user Full Control. However, when she clicks on the item, the display form now states that she doesn't have access to the page.
This might happen when "Limited-access user permission lockdown mode" feature is activated in the site collection. In my case, it worked when I turned that feature off.
For more information, you can read at MS Article