USB Speaker keeps rebooting after MacOS shutdown

OS: MacOS Big Sur (OpenCore)

CPU: i7-9850H

It's a mini PC (NUC alike).

Hi, After I shutdown MacOS system, it seems everything is off and the power led changed from blue to red (this is correct). But there is only one problem. I am using USB speaker for audio. I can see the USB speaker keeps rebooting itself forever after system shutdown. To solve this issue, I have to unplug the PC's power. Even if I reconnect the PC power after unplug, the USB speaker is fine too.

This is kinda weird. I can see my SSD is shutdown properly with smartctl. I don't know what else I can check. Do anyone have any ideas how to fix such issue?

Thanks a lot.