Login and Logout dont work unless i clear my browser cache

[kerrinbanner]

login and logout are not reflected in pages on my Zenbership site unless i clear cache.
Once i logout , i can still see all authentication protected pages until i clear browser cache then reflected correctly.
The same is true if i login, all pages tell me i need to login bit once i clear browser cache i can then click on page links and navigate there successfully.

I have version 116 but upgrading would not be an option.