Hi Arnold,
Something is wrong, but I have no idea why 
You share ACCOUNT and ACCTDETAIL dimensions for both models and the records can't be affected by XDIM_MEMBERSET on ACCOUNT.
For the simple REC(EXPRESSION=%VALUE%,...) the multiplication can happen:
1. If you SKIP_DIM some dimension and scope this dimension for multiple members. Not in this case: *XDIM_MEMBERSET ICDATASRC = IC_INPUT - single member!
By the way, the code can be:
*XDIM_MEMBERSET ICDATASRC = IC_INPUT
...
*RENAME_DIM ICRENTITY = ENTITY, ICRINTCO = INTCO, ICDATASRC=DATASRC
...
*REC(EXPRESSION = %VALUE%, ICRENTITY = ICRENTITY.LEGAL_ENTITY, ICRINTCO = ICRINTCO.LEGAL_INTCO, ICDATASRC=DS_INPUT)
2. If you override target of number of records with the same member:
ICRENTITY = ICRENTITY.LEGAL_ENTITY, ICRINTCO = ICRINTCO.LEGAL_INTCO
Same values of properties: LEGAL_ENTITY or LEGAL_INTCO
Vadim