Are you experiencing disconnects and freezes with USB 2.0 devices on your new MacBook Air or 13-inch MacBook Pro? Well, you are not alone. Apple is yet to recognise the issue officially, but there is a workaround for the time being.
https://www.notebookcheck.net/Experiencing-disconnects-and-freezes-with-USB-devices-on-your-new-MacBook-Air-or-13-inch-MacBook-Pro-There-is-a-workaround.477327.0.html
The "Caldigit TS3 plus" works. Don't bother getting the official apple dongles as these don't work either.