You should also be aware of this fix in 01.05.03.00:
QTI9X50-837 Fixed issue when downloading FW in Linux using USB 3.0 FW DOWNLOAD
If possible I’d recommend connecting the modem by USB2 when upgrading from an older firmware. Use an external enclosure with a USB2 cable, or temporarily cover the USB3 pins if you have no other way to disable USB3 on the m.2 slot.