Dataloss issue with this lambda redshift loader

Hi,
We have faced data loss issue with this setup and had to go with a different approach. Looking forward to get the issue fixed.

We have done all the set up and was working fine with relatively less data. We used the reprocessBatch approach for firing the copy command for failed files. It worked well in lower environment . But in production, with the large volume of data we faced dataloss of 850 million record out of 23 billion records. We had made sure that the failed files are reprocessed.
We didn't get any error also.

Thanks