We bought a new Santa Fe in Navan in 2014 and traded it in 2017 for a second new one. The timing chains were not an issue in either vehicle- But the oil service interval is quite long and both the Santa Fe's have to be brought in every 6 months for an oil quality check-which we always do and if oil is not up to scratch its must be changed early. This is in addition to the annual required oil change of course. I think the engine oil lubricates the timing chain so oil quality would be important to keep the chain lubricated in accordance with manufacturing specs.
If those 6 monthly oil quality checks were not done by a main Hyundai dealer, nor the engine oil & filter changed with the recommended oil/filter by a main dealer and - then I wouldn't blame the Main dealer or Hyundai for voiding the warranty.
At the first full service of our 2017 Santa Fe the oil filler cap was not replaced properly and the oil seal failed and car died on the road suddenly luckily without any safety issues, but leaving a huge trail of oil on the road and I was sure the engine was kaput. Hyundai towed it to main dealer and examined engine and advised that it was OK as ECU cut out the engine before any damage occurred and its run perfectly since then. But dealer advised they would have replaced engine under warranty without issue. The vehicle was a year old then.
Great cars to drive I think as the Santa Fe is my wife's car and my old 2010 Honda CRV (215kms on clock) drives like a dog compared to her Santa Fe even though both are 2.2 diesels.