Inland Marine Coverage as All Risk

Our insured operates a stone quarry and has a stone crusher covered under an inland marine form. The motor that pumps oil to cool the main motor failed, causing the motor to run without oil. This caused the motor to overheat and seize up. The crusher has fail-safe devices meant to prevent such damage, but it has been determined by an investigation that a metal conduit housing an electrical cable for fail-safe devices had been crushed. This caused the wire to either sever or short-out and made the fail-safe devices inoperable. The cause of the crushed conduit is unknown, but could probably have been caused by a rock or some other object hitting it.

This IM policy is on an all risk basis and we think the loss to the crusher should be covered. What is your opinion?