Hi Dga,
We have the same problem with our gld-80 and our gld-112. the fx still functions you just can’t control its volume level or mute it. There is no way to get the fader back other than re-loading a show file that hasn’t used the fx rack. I have submitted a ticket to A&H support about this before but I suggest you do it as well. You can however send the channels to a group and then insert the fx on the group so that you have a volume control and a mute(using the group).
Hope this helps,
Paul