This is a fundamental engine design issue in their popular Theta II engine that results in premature and excessive wear on cylinder wall, leading to excessive noise, vibration, stalling, and ceased operation.
In a quest to save weight and increase power, they made connecting rod too thin and height of the bearings too narrow to hold unwanted movement of pistons in check. Instead of piston moving just up and down, there was sideway play often resulting in severely scratched cylinder wall after 15k mile of driving. There are many reports of connecting rods grenading altogether.
For those not familiar with engine parts, here it is. https://image.slidesharecdn.com/sixstrokeengineppt-140826102...
Hyundai found out about this pretty quickly, and de-tuned engine output in later iterations to increase reliability. Yet, they have consistently denied this design defect as a problem for many years.
There already has been multiple massive class action lawsuits and recalls on this in the U.s. since 2015. Many Korean customers were angry that Hyundai was not issuing the same recall in their home country, where they often pay higher price than identical exports.
http://www.pbs.org/newshour/rundown/hyundai-kia-recall-engin...
The only fix that will 'stick' is complete engine replacement.
I hope Korean customers get the same treatment.