Thanks! Could you be more specific of how I should instruct the LH agent?
As I understood it, they have to refund the rail and fly part, and leave my lifemiles award as it was orginally. Then create a new booking and ticket -- this is the part that confuses me the most-- (from where to where? could you give more details) and then onto this ticket add the rail and fly?
Would going to the FRA train station work?
You create the route when you check-in with DB, the LH agent only creates a PNR and e-ticket number.