Mr.Smith was very disappointed to see the car【that】 he had had ______ went wrong again
这是that引导的定语从句,修饰前面的the car,that在定语从句中做had的宾语,相当于：
【had that repaired.也就是你说的had sth done】
that引导定语从句的时候,如果that做定语从句的宾语,【that可以省略】.所以你看到的是had had repaired、