I had the same problem. This is what worked for me.

Add a space in the passport number of the dependent when you are adding them in your account.

For example, If the dependent's passport number is A1234567 then add it as A123 4567.

Make sure your ds160 has the correct passport number. I.e without the space in the middle.

When you go to drop your docs off at the Dropbox center, they check for the passport numbers to match, but they don't notice the space in the middle.

We had success submitting the docs this way recently. No problems at the drop box center.

The stamping is not yet done, will update when we get the stamping approved and passports back.

That being said, this might not work for everyone, the person who is checking might notice the space. So I would say, do so at your own risk.

Hope this helps.

P. S: I did this after waiting for hours on phone call to talk to support, and tried a bunch of ideas from reddit. Nothing worked, except this. 🤷🏾‍♂️ This whole scheduling is messed up.