According to Whatcar? the most reliable in this class was the Z4 (2009 - 2016), the car with the most faults was the Mercedes Benz SLK diesel (2011 - 2016)
https://www.whatcar.com/news/most-reliable-type-of-car/?utm_medium=EMAIL&utm_campaign=enews%20bulletin&utm_content=WCAR%20Enews%20bulletin%20-%20(09.06.2018)::Readme2&utm_source=20180609#4
https://www.whatcar.com/news/most-reliable-type-of-car/?utm_medium=EMAIL&utm_campaign=enews%20bulletin&utm_content=WCAR%20Enews%20bulletin%20-%20(09.06.2018)::Readme2&utm_source=20180609#4
:thumbsdown: