After your 700 mile trip and heard the glass rattling in the fire place I decided to end that noise once and for all.
I removed the 4 screws that mounts the whole unit to the cabinet.
I them removed the right sidebar which is held in by 2 screws.
Slid the glass out and took some rood rubber electric tape and place a continued piece all the way around the four sides of the glass and folded the tape on the front and the rear evenly.
Slide the glass back in and put everything back to gether and no more rattling.