Doing Validation for File Input (XML upload) for my custom BO

I'm developing a File Input Integration (.pid) and I need to do validation on the fields against the master data

For my custom BO, I have put some ABSL code in the Validation-OnSave event.

It checks to make sure the Account ID is valid against the Account BO.

If invalid, it returns false and raises the "E" message.

The problem is that I don't see the errors in my logs or anywhere.  The records are not saved in the BO, which is good.  But I don't see any errors - either in the log or the Business Communicaiton Monitoring.

On good batches, the records do get saved.

Has anyone tried validation in the File Input  ?

Should I turn on "Mass Enable" on the Validation On-Save event ?

Appreciate your help !