Hi David, sorry to hear your problem.
When contacted, the support told me to put some grease on the vertical screw. They recommand the “Magnalube-G PTFE” grease, but i can’t find it here in France so I put another PTFE-Teflon grease that i used in airsoft replica. You can find it in DIY store or Amazon. Just put some grease in the lengh of the screw and you will be Ok.
It’s a little bit annoying to have to do it ourself and lacking of information about this.
For the DFU I got the same problem, i think i changed the usb (and plug it in directly in the PC) and it worked. There is another informations here: "Could not open DFU device" with trying to update firmware
If you continue to have problems, feel free to open a ticket. The support is very reactive!
Hope this help.