You can use the data access API to retrieve records that have failed validation. 

Firstly find the batch ID that you want to retrieve from the AEP UI:

Then run the first request using that batch Id, it will retrieve the URL path to retrieve the original payload along with details of the validation error.  

Now run the second request to retrieve the details. 

Query Service

Data Access API

emea_hol_api_credentials

emea_hol_sandbox

sacker-BUFY?token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImFub255bW91c

emea_travel_bootcamp_website

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6ImFub255bW91cyIsImVtYWlsIjoiYW5vbnltb3VzQGFkb2Jl

emea_carvelo_hol_website_token

https://dsn.adobe.com/p/carveloHOL?token=

emea_carvelo_hol_website

emea_travel_bootcamp_api_credentials

apac_travel_bootcamp_sandbox

apac_travel_bootcamp_org

SB21 - AEP Bootcamp - Cross-channel Data View