Originally Posted by wolftail
However, as Cscat said, items within submenus appear only the first time they are opened. After that you need to restart the framework in order for them to appear again.
This affects JSON menus only, and I'm unsure why this is happening. Workaround: label it as a dynamic menu in the config.xml, i.e.:
<menu type="json" dynamic="true">menu.json</menu>