I was attempting to flash my V20 (F800S model) with LGUP and Uppercut some days ago. The flashing got to 12% then stalled and eventually timed out and stopped completely after an hour or so. Tried it again, and got the same result.
I then disconnected the phone from the PC and force-shut it off. Since then, I instead get the error 0x81000302 in various flavours when I try to flash the phone.
If I use Uppercut combined with LGUP, I get the message "Error: 0x81000302, Please use latest DLL. LAF Protocol version is not match".
I've also tried using LGUP alone without Uppercut, instead using a DLL for the device. I extracted the file LGUPc.dll from the KDZ firmware I was trying to flash with, renamed it "LGUP_common.dll" and placed it in the LGUP\model\common folder. Then, as I again ran LGUP, I got the error "DLL for F800S10e is not installed properly. Please install a DLL package (*.msi) for the model."
I then installed a common MSI-packaged DLL I found online and tried again. That gave me the error "0x81000302, AtCmdTxRx Error".
Any ideas what to try next? Since that initial flash failure, the device has been booting straight into the firmware installation screen, and can no longer boot into Android. Really hope there is a solution that could bring it back to life!