It is not unusual for airlines to be very stubborn in situation like this and only offer a (full) refund (and refusing to rebook to other carriers despite being obliged to do so under EU Reg. 261/04, because of the costs connected with such rebooking). Therefore, you most likely end up in a situation where you are forced to purchase another ticket on your own (book the cheapest available) and seek reimbursement from Saudi afterwards. If you intend to do this, do not under any circumstance accept a refund of the existing ticket, as then Saudi will be off the hook/no longer under a duty to reimburse your new ticket.

Obviously, this approach is risky as Saudi is likely to refuse to reimburse afterwards and you will be forced to escalate in court or with the competent public authority.

If you do not want to spend time on and costs fighting this with Saudi, you accept a full refund and move on.