Enabling ScriptManager PageMethods doesn’t work in some scenarios in SharePoint 2013

I worked on a case where the problem was that PageMethods won’t execute from within a SharePoint 2013 application page (page deployed to the _layouts folder).  To replicate the problem, I had a custom master page deployed through a VS 2012 solution with the following definition within the <body/> element. <asp:ScriptManager id= "ScriptManager" runat= "server" EnablePageMethods= "true" EnablePartialRendering= "true" EnableScriptGlobalization= "false"...(read more)