speaker problem even if I changed it it still has problem

Good evening, im a macbook pro mid 2014 owner. One year before i noticed a weird sound on my macbook pro left speaker something like cliping at the high frequencies. Its hard to explain i will post a video with the hope tou help you understand it. So i went to greek authorised apple service they replaced it and everything was fine but only for six months, after the problem came again. And now i dont know what should i do i went again to the service but they cannot find what caused it. So what do you suggest. Its not a problem for me to pay again 120 euros for replacement but would be a problem for me if this happen again. I hope that someone can help me. Thank you in advance and happy new year.

PS dont forget to check the video for further help about my problem,

https://youtu.be/8IaPbYsDgro