Sorry for the delay. I'm unfortunately unable to post an anonymized ETL at this time.
We were accessing a bucket using the S3 protocol with the UniversalDataReader. The ETL needed to read the contents of all files that matched a particular pattern. Previously, we had been using the * character as a part of the pattern and it had matched the files appropriately. At the time of posting, S3 had started regarding the * character as a literal rather than a wildcard, so none of the filenames matched the pattern that I had set up. So, for example, rather than finding all files that matched the pattern 'ABC123*.txt', the S3 protocol started telling UniversalDataReader that there were no files with the name 'ABC123*.txt'. Since UniversalDataReader recognized the wildcard even though S3 did not, the ETL did not error and we had a process that was quietly failing.
We managed to work around this by accessing the bucket via HTTPS, but that's not ideal when there is a dedicated protocol.