The "wet belt" is a known issue with the Euro 6 Transit Custom with Ford recommending it being changed every 10 years or 144,000 miles. A number of examples have seen failure before this mileage and a lot of independent garages recommend changing them sooner - at six years or 96,000 miles. As this one has had the belt replaced and associated repairs carried out then it's arguably a safer bet than a van that hasn't so this is generally a positive thing - just be sure to keep on top of belt changes in the future and replace it before the manufacturer-recommended interval if you value peace of mind.