Hey after seeing them live last year I noticed that they skipped this part and went straight into the last verse.

I mean the part at 5.33: https://www.youtube.com/watch?v=3y_o0S5uOvE

I love that backways style and the way shift back to "normal" again. but im dissapointed at them for not playing it live. Cant find any recordings after the Binge & Burge 89 and some bootlegs from the same tour where they actually played it.

I have not seen anyone mention or discussing this either. I mean it cant be that its to challenging for them with 30+ years of expierience to count 5/8 and 7/8.

What do you think? AND DOES ANYONE KNOW WHY????
I wouldn't give it too much concern. I saw them a few years back, actually when Death Magnetic came out. At that show they played most of And Justice For All including Blackened and One, most of Ride the Lightning, and most of Master of Puppets in addition to playing a lot of their new songs. They nailed every one.

Anyone can say what they want about Metallica, but they do put on a hell of a live show and haven't missed a beat, including their older toughest songs. I don't know why they wouldn't have played it in your particular reference.