Imported balances being removed with subsequent import

Summary

Using DM to load data into ARCS is failing to populate multiple profiles with correct balance data.

Content

We have inherited the system setup by a partner and are having some issues with the way the data is getting/or not getting loaded.

We have multiple .csv files for different entities that need to be loaded for the same period using the same load rule.  We have manually uploaded the data into the staging table in DM.  To keep things simple we loaded one and then appended another...in the staging table we could verify and view all the data from both files loaded successfully.  From ARCS we go to the period (import data) for where this is to be loaded.  Only one of the two entities is loaded with the balances.  Why are we not seeing all balances from both files being imported to