"Upload translations" via web only triggers if you click on the Plus sign or the text "Add..."

From a project page:

1. Select a version
2. Select a language
3. Click the chevron next to a document
4. Select "Upload translations" from the drop-down menu
5. In the "Update translations" modal, click on the Add button, but not on the plus icon or the "Add..." text

Expected:

1. The button changes appearance to show it has registered the click
2. The file selector ("Open Files") should appear

Actual:

1. The button changes appearance to show it has registered the click
2. Nothing else happens