While we don't have a clue ... a good guess would be that the truss system for one part of the roof did not align with the trusses from another part of the roof. In many areas, that angular piece would be conventional framed (hand framed, whatever) between the two sections of the trusses - this would be specified on the truss drawings as to what went where, but if the 'hip ledger' (for lack of a better term to describe a ledger installed alongside a hip truss to support other framing and the roof sheathing) were installed to low, then just what you see would happen.
One of two things happened.
1) One side was lower than the other side.
2) The other side was higher than one side.
The builder should correct it, not through a structural engineer, but through his truss engineer.