I encountered this repeated issue, but only while intentionally trying to wipe and reprovision 1 of 2 M4 MacMinis in our lab; it wasn't while using the Mac e.g. streaming video as you mentioned. You may rightly have a hardware issue.
But even in known-good hardware scenarios, it seems there's an issue restoring/reviving M4 MacMinis via Finder/Apple Configurator, resulting in errors such as these...
[Apple Configurator error]
The System cannot be restored
on this device.
Gave up waiting for device to transition from Port DFU state to DFU state.
( Stop )
or
[Finder Mac Recovery Mode error]
The Mac "Mac" could not be restored. An unknown error occurred (21).
( OK )
As you indicated, repeat attempts restore or revive all fail. I was prepared to contact AppleCare enterprise support, but thought I'd try one last thing first.
A post in a private MacAdmins Slack channel mentioned that the MobileDevice framework and can be updated independently of the OS and should be included in both Apple Configurator.app (AC) and Xcode.
I was already using a newer release of AC—which was failing—so I thought I'd grab the latest Xcode.app version compatible with macOS 15.5 (omitting version details to avoid NDA, but any publicly available Xcode version should suffice).
After installing Xcode.app, launching it, clicking the registration prompt, etc and closing Xcode (not directly being used in this case), I put the M4 MacMini back in to DFU and retried AC and...
It actually worked!
I know it seems unlikely and the 3GB download took its sweet time. But, I'm glad I don't need to contact AppleCare or swap out this M4 MacMini.
Hope this helps anyone else encountering this issue.
Notes:
- I did see periodic prompts to allow USB device/adaptor (likely due to an Apple USB-C/A adapter I had plugged in).
- macOS Sequoia 15.5 was used in both target and host Macs.
