My Scarpa boots have come apart at the Achilles region, both sides, This would not matter too much except that the blue anti-blister patches come off when the upper and lower sections come apart. There are a few options.
The inners could be stitched to the outer leather, but the leather is very tough and may be hard for an awl. The local cobbler is no use. Second, glue the two parts to the layer underneath, a soft black foam that may not be strong enough to resist the stress. Third, glue a thin patch over the tear.
Advice about which of these or a combination would be valued.