Under Mathematica 10.3 I had customized the context menu to include "Copy as Bitmap" for "GraphicsBox" and "Image" selections by inserting a line
MenuItem["Copy as &Bitmap", FrontEndExecute[ FrontEndToken[FrontEnd`SelectedNotebook[], "CopySpecial", "MGF"]]]
in the appropriate places in the file $InstallationDirectory\SystemFiles\FrontEnd\TextResources\ContextMenus.tr
The same does no longer work under 10.4. What has changed? Has anybody else had that problem?