The subsidy shall be paid in the installments the Department of Transportation and Public Facilities thinks proper, after proof is submitted that the conditions of the contract or subsidy are fulfilled up to the time of payment. The inability to touch at a point along the route designated by the department due to a lack of proper docking or harbor facilities or to stress of weather does not prevent the owner or charterer from receiving the money otherwise earned, and is not a cause for reducing the amount of the subsidy. If the subsidized vessel is lost, wrecked, or damaged, the department may permit the contractor to carry out the service temporarily with another vessel or ship of American registry that meets with its approval.