Hi rschoop,
Can you please provide timing diagram of Clock, frame sync and Data as expected by external device for its operation? By looking at the information you provided in the thread , I believe sport in multichannel mode would be better for your application. For more information on sport mutichannel mode please refer to Sport chapter of HRM.
In framed mode, you need to have frame sync for every word.That may be the reason for receiving Junk data.In unframed mode ,first frame sync initiates transfer after that sport will receive data continuously on every clock. So this may be the reason for mismatch.
Regards
Sachin