Warped Stelvio Pannier

The left hand plastic pannier on my Stelvio is warped and the lid will not seal properly. It appears to be the back part that has bowed and no longer meets the front and back of the lid.

My theory is that the heat from the exhaust has allowed the pannier to deform at the cut out section. Has anyone found this and being able to rescue the situation?
I am guessing that the back part will not be available separately.