Users are randomly receiving the message, such as "Your request could not be completed because you have been signed out" in AEM.
While using the out of the box 404 page, the problem occurs in specific conditions, for example, running on publishing instance, accessing a resource that does not exist, and there is no specific authentication mechanism available. In most customers instances, there is a customized 404 page that overlays the out of the box 404 page. Thus, these customers do not see the stated problem. For customers, who come across this problem, the recommended solution is to overlay the out of the box 404 page by copying the 404.jsp from /libs and placing it under /apps.
To fix the problem, overlay the 404.jsp page.