It looks like there are many Windows Insiders that got their smartphones bricked while they were trying to recover them using Microsoft's Windows Phone Recovery Tool.
The issue is known as QHSUSB_DLOAD because this is the message those affected by the problem are getting when they attach the smartphone to the PC.
Unfortunately, there's no recovering once your smartphone is recognized as QHSUSB_DLOAD, which means the current Windows Phone Recovery Tool needs to be updated so that it can fix this issue as well.
As NPU points out, Microsoft is already aware of the problem and is now working on an update to Windows Phone Recovery Tool that will allow those with hard bricked phones to recover them.
There's no known workaround for the issue
Here is an excerpt of the response one of the users affected by this issue has received from Microsoft on the company's support forum:
“We’ve heard similar feedback from a subset of Insiders working with Windows 10 Insider Preview for phones where an error impacted their phone.
“Through this feedback we are investigating the various user end-states, including the QHSUSB_DLOAD error some have reported, as well as other issues that don’t have detail or exhibit different symptoms.
“Our Windows Phone Recovery Tool team is actively working on an update to the recovery tool flashing process to help with corruption issues.”
There's no ETA for the release of the updated Windows Phone Recovery Tool, but we hope Microsoft will be able to offer a proper fix for those affected by this nasty issue.
Furthermore, Microsoft advises those affected by QHSUSB_DLOAD error to follow their forum for any updates as they are working to address the issue.
We will also keep an eye out for any additional details on this issue and will update the news once Microsoft offers another statement.