Apple not living up to its reputation

I have just hit another "sticky key' on my macbook and am so frustrated. I bought an Apple Macbook in the USA in December 2018. About 6 months later, I began to have trouble with the keyboard and after some research discovered that this model has "sticky keys" and that the warranty was extended for this fault. Nonetheless, I sent my computer in for repair before the warranty expired and to date I have sent it in 5 times. 4 times in South Africa and once in the USA when I was there in December. The keyboard has been replaced 4 times and I have been told that the issue has been dealt with yet within a week of getting my email back the problem starts and then becomes progressively worse. When I finally told the local Apple store that I could no longer keep on sending my computer in for 2 weeks only to have a repeat of my past experience I was told that they cannot do anything for me as the computer was not bought from them. I thought that Apple had a world wide reputation for excellence and am at a loss on how to deal with this so that I can continue to use my computer problem free.