I have this site structure using a clean OOTB Publishing Portal and May 2015 CU:

    WebA
     ->WebB
        ->WebC

and a user "UserA".

UserA has been granted "contribute" permissions on WebB which has unique permissions. WebC inherits permissions from WebB and UserA can see WebC in All Site Contents and access it. Navigation settings for WebB and WebC are:

    Global Navigation
    [x] Display the same navigation items as the parent site
    [x] Show subsites
    [x] Show pages
    Max number of dynamic items: 20


**The problem is:** UserA cannot see WebC in the navigation from both WebB and WebC. If however I go in and untick Show Pages on WebB it suddenly appears. And now its there even if I go back and re-tick Show Pages again so some update has occured.

I don't want to have to open the navigation and modify it to force a navigation update. Can someone shed some light on why this is happening?