Reviewed closer and tested locally and live. I could not confirm your issue. Whether PM or Email I received the notification successfully with a subject and body. Being language strings if you defined them as empty this could result in an empty email or if your hosts mailserver is post-processing the emails before sending this too could be a reason why they're empty. At any rate I see no issue with the notifications as from they need to use $myId for the From so it is known exactly who edited instead of always the group owner.

Then the notification is not coming from GJ it would seam. I can not duplicate your issue nor does it seam even possible reviewing source. Please check that the language string has not been defined as blank of the notifications.