Mail context flip-flop

On the mail app, if I am looking at an unread msg in a folder, pressing the ‘down’ button takes me to the next msg, but the context-sensitive toolbar switches from ‘Edit Document’ to ‘Navigate View’. Pressing the ‘down’ button on that toolbar then switches it back to the ‘Edit Document’ toolbar. Pressing ‘down’ button now moves to the next msg, where the cycle of context switching begins all over.

This does not happen if the msgs are marked as ‘read’.

Mail app uses the StdR851Mail template as delivered.