Sandisk Extreme 480GB SSD on Macbook Pro 15 inch mid 2012

So I ordered the same model from Amazon and it’s sort of giving me the same problems with starting up with the white screen and the flashing folder with the question mark through it but the only difference (good difference) is that when I go into disk utility while beginning the computer holding option, is that it always recognizes the hard drive and I just have to set it as the start up disk.  I am going to return the original one to Amazon today.  But why it occassionally doesn’t select the hard drive to start up is still not clear.  It could just be the firmware as you say.