SSAS : Error with many-to-many dimension and level of granularity

In this blogpost a brief explanation of an error i've encountered during a implementation of a 'many2many relationship' in a SSAS cube. Although i haven't found the rootcause of this problem i do want to share with you the solution. I did only found one relevant website of Melissa Coates with the same sort of problem. So hopefully this will help the MS BI community a bit futher.