EM12-G Firmware Flash failing DL_Firehose timeout

I am trying to flash my EM12-G module and receive the error message “FAIL, DL_Firehose, Time out!”.
I already tried on 2 different computers with additional power supply attached.
The current Revision is EM12GPAR01A04M4G_MSFT and I want to flash to EM12GPAR01A21M4G_01.009.01.009 and I am using QFlash_V5.9 utility.
I also tried in “Sahara” mode, but then I receive error “FAIL, Detect SA download timeout!”.
Please help me, because the modem is not working…

Hello, your current direct upgrade from A04 to A21 span is too large may make mistakes, suggest you find a middle version, such as first upgrade from A04 to A11, and then upgrade from A11 to A21, I hope it will help you, and be sure to ensure that the module power supply voltage is stable, I hope it will help you, thank you.