The problem was, that my Surface right speaker, sound less than left speaker and also it sounds with less highs than left, so I assume that iut was Hardware related. But otherwise, my unit was perfect, onlu a little movent on the locking button but overall OK.
The time to get my money back expires on Sunday, so I don't want to exchange it for another the last day, and if the new one have problems, only had 1 day to return it.
Maybe Microsoft solves the issue of low volume, and maybe it was only software, my problem, but when everything is fixed, I will bou it again, and exchange it as many times as I get a barely perfect unit.
Every day all the quality control get's worse, for some people is the same, and they don't have problems with loose volume buttons, or backlight or something, but for me, as I'm buying a premium product with premium price, I wan't PREMIUM QUALITY CONTROL.
Come on Microsoft, the product is insanely awesome, fast, looks god, connectivity,,,, Try to fi this problems, and it will be a best seller, also for the people who cares about quality control.