Pajero V60 control chain torn at 78000 km

Hello municipality, with my Pajero V60 DI-D, automatic, BJ 2003 the control chain is torn at KM-Stand 78000, according to m_händler the fuselage is ok, the head has to be renewed, the estimate is 6500.-€. 2008 in Nov. the head seal was renewed and the head was planned, the control chain was installed out and again. I know that there is an internal paper at Mitsubishi, which when the chain is installed the engine can not be turned counter-clockwise in any case, But it seems to have happened here. The question is that you can prove something like that and is it basically allowed to plan your head with the DI-D or does it have to be renewed? Anyway, I am sitting on the damage and my dealer only twitches with the shoulders… bad luck? …that can’t be! Who can help me?