EM12-G firmware upgrade and USB3.0

Today I was about to update EM12-G firmware from EM12GPAR01A18M4G to EM12GPAR01A20M4G using USB 3.0 adapter and Qflash V4.20 on a Windows 10 PC with latest Quectel LTE/5G drivers.
I followed the instructions in Quectel_Qflash_user_guide_3.3 A.pdf setting up the DM COM port.
When I press the start button, Qflash tries to communicate with the COM port, it seems ok, after a couple of seconds Qflash tries to open a “virtual port” and the device disconnects; 60 second countdown but no virtual ports were found.

Could it be that firmware upgrade via USB 3.0 for EM12-G is not supported?

I found that flashing Quectel modems on a USB2 interface is more reliable… your mileage may vary.

I already flashed another EM12-G via usb 2.0 adapter some months ago and it went well at first shot, now I have only a 3.0 adapter and it doesn’t even start, that is the reason I ask, I’d like a confirmation to avoid unnecessary work and resources.

What’s a good USB 2.0 module to use to flash the EM12-G?