Can we use Sales Order in reference field instead of RMA while Importing CM through FBDI

We need to Import Invoice and Credit Memo using Sales Order in the Reference Field through FBDI. However,

we are getting error: Each line must have a unique combination of INTERFACE_LINE_CONTEXT and INTERFACE_LINE_ATTRIBUTE values for the transaction flex field.

We are getting error since we already created Invoice using the same Sales Order number in the Reference field:

INTERFACE_LINE_ATTRIBUTE1