Around 2017/2018, the National Visa Center (NVC) took their "document review" process digital. Previously you would have to mail in all of your documents, wait 2-3 months for your documents to get to the front of the line, they would verify them, and then after they were verified would send the "okay" to the actual embassy in the country you are applying from (in our case Taiwan).
If you had an issue with one of the documents, you would repeat the process including the 2-3 month wait. This makes sense, since when receiving mail you'd have to actually "process" it first to see if it was for an existing application or not (instead of just putting it in a giant bin for "July 15th").
When they moved the process online, however, they kept the same queue process. You wait 2-3 months to get to the front of the line, and if there is an issue, you have to resubmit the document and wait 2-3 months for them to review it again.
It's fairly easy, however, in an online format to tell _who_ each document is for. What _should_ happen, is you are put in a queue and have to wait your turn to get to the front, and then they work on helping you get through. If you have an issue with a document, you resubmit and it's looked at next to get you "moved on through".
They also shut down the phone line that you can call to talk to an actual human being about what needs to be submitted. Instead, you can submit an email that has a wait time of 2 months to get your question answered.
Overall one of the most frustrating experiences of my life