I have the same problem.
I've done a short circuit and then my Mac din't recognize my Duet WiFi.
When I plug the USB cable U11 get very hot, so I've decided to replace it. I'll let you know if my repair works
Hi everyone, I solved this buying a silicon cover for the heat block (as Phaedrux mentioned) you can get some pretty cheap on Ebay, I also realised that you don't need to have a E3D hotend, they are not available for every hotend, but you can found for the most common. With this the temperature only goes down 5 degrees and in a few seconds it's in the desired temperature again.
Thanks everyone!
