seeing what happened on the casing it is clear that after slipping on the sand the bicycle continued to slip and the sidewall of the clincher has been abraded during the contact with the floor.
It has been like if you’ve filed the clincher with a big wood file, in fact as you can see it’s been completely chewed by the asphalt, on consequence the inner tube has exploded because there was no more tissue able to keep it inside.
On our side seems that there are no production faults but this is only the consequence of a bad fall.