Here's what happened to mine. About half way between the front axle and the front of the trailer the main frame members were butt welded together. Unfortunately the bead they ran missed the joint for about half it's length. This was on the driver's side. This was in 2012. My trailer is a 2006 FSAK 26.
I took these pictures and sent them to Attitude. They put me in touch with Lippert. I had a mobile welder come to my house (I didn't dare drive it anywhere) and he welded the joint and then welded a plate over the joint to reinforce it. He charged me $500 I think and I sent the receipt to Lippert and they reimbursed me. He did both sides of the trailer just to be sure.
I have also had the center spring hanger on the passenger side develop a crack in the weld to the frame, the rear outrigger on the passenger side rotated down and caused the side of the main frame member to develop a crack along the bottom of the outrigger. I was on the road and once again had to get a mobile welder to come out and fix the trailer. I don't remember what that one cost. I had photo of this but I can't find them right now.
Fred
Mod Edit: Changed width to 640 instead of height at 640
2006 Attitude 26FSAK
1997 F-350 Powerstroke
1993 KTM LC4-400
Me
Wife
12 year old son
12 year old daughter