Hi Lukas,
i'm not aware of any tracing tools for the MDX provider, but there is an SAP Note supporting it. there isn't much in it since the code may actually be OEM'ed from another company and SAP is simply reselling it.
when you see the row count mismatch, is there also a difference in the amounts, i.e. sum of amounts across the two rows does not equal the amount (sum) on the single record? i'm assuming there's no additional attribute that would make the groupby results different between the two clients.
Thank you,
greg