I don't know that it is a fight, they have offered a settlement.  I'd politely refuse their offer, stand pleasantly firm on 100% of your costs, and assure them that next time there is an issue you will also expect them to fix any issues, including all repair parts and labor costs and some liquidated damages costs for unnecessary downtime, until and unless their line meets all height requirements. 

That's exactly what they would do to you because it is just business, and you should treat it as just business.  It's not personal, you would just like to get made whole for a situation for which you have zero liability and they have all the liability.