I am currently experiencing a very unusual issue with a SharePoint 2013 on-premise. We have done performed a migration from SharePoint 2010 to SharePoint 2013 and when logged in as a user who is not a site collection administrator they are seeing the message "Sorry you don't have access to this page".
We are currently finding however if you click black in the browser and navigate to the same page again then the users can access the page fine.
We have give all users read permissions to the master page gallery and everything is checked in, published and approved.
I have seen a few posts about user accounts not using claims authentication and we have run a script convert the user accounts however we are still seeing the same issue.
Any help would be greatly appreciated.