Interesting issue. I am creating Page Layouts in Visual Studio 2015 for SharePoint 2016 (with Visual Studio Tools preview 2) and when I deploy the solution in Visual Studio and create a page, I get the "Only Content controls are allowed directly in a content page that contains Content controls."
But when I upload the .aspx file directly into the Masterpage Gallery, it works fine. What could be the issue?
Bismarck