In case anyone else has a similar problem, the solution is:
- Remove Account selection from the idoc input schema.
- The input schema for the idoc needs to be your Customer table/Row Generation
- Add the Account selection to the relevant segments.Do not select from Customer here
- Do not use a join (this is where my problem was). If you use a join, you are required to select from both Customer/Account tables, which causes the problems I had
- Use the where clause with something like Customer.ID=Account.CustomerID (or whatever your join condition would have been)