Since you have mentioned that everything was working fine till last week and nothing has changed I am not sure what is going wrong. But normally this error happens when the AEM doesn't sent the CSRF token along wiht the request. Jorg has answered a similar question here . Check if this helps
Can you check that a CSRF token is actually sent to the dispatcher? Can you enable debug logging on dispatcher and see if that header is transferred to the publish? The header name is "CSRF-Token". If it is not there, include the "CSRF-Token" under clientheaders in dispatcher config file.