The responsibility for the cost of repairs will depend on the nature of the breakdown.
For breakdowns caused by mechanical failure or wear and tear, the owner will be responsible for the cost of the repairs. They will also be responsible for retrieving their RV from the repair shop in case the renter is unable to do so.
For breakdowns caused by the renter's actions, the renter will be responsible for the cost of the repairs. They will also be responsible for covering the RV owner's costs to retrieve the RV, in case the renter is unable to do so.