[G3 General] Hnk1:
I assume you are using the same TWRP version and both of them are same models.

I did some tests on my LGs which I got recently. Lg g4c , Lg spirit LTE single sim and dual sim LTE and Lg G4 mini.

I buy used cheap phones from ebay / friends and then fix them. I enjoy the challenge simply!

In this purchase, Lg Spirit dual sim variant H442 was only able to detect LTE and sometimes WDCMA but it could ONLY connect to 2G (GSM) so I made all the backup and then flashed LG g4c QCN (both share same hardware) and viola, 3G started to work flawlessly however, LTE was no more detected in manual search. I flashed other QCNs from G3 G2 etc but it use to break signals fully as different chips are used but flashing from same company (Lg to Lg and same snapdragon 410 worked)

So I when I flashed my previous H442 Qcn, it would still break LTE and nothing was detected in terms of LTE but as before only 2g worked and i could search 3g but could not connect to it. Thus, I lost LTE completely after it. No detection even.

Then i restored my backup using EFS Professional and viola, LTE was again detected but could not connect. So every time I had to experiment, i had to restore the partitions and then flash QCN else it would further break my connectivity.

As I stated before, it is more than Qcn which is responsible for LTE and other basebands signals.

As for G4c, i have 3 devices. Exactly same models h525n.

However, they didnot have any connectivity issue. (1 europe internationat, 1 with vodafone/orange bloatware and last one I converted to international from voda hungary).

One of my device had some error (location error and region error) which was not fixed by kdz method or hard reset and thus I flashed partitions using EFS professional from another device and everything started to work apart from voda boot image that started to show which was before of Lg.

I skipped system,cache and userdata partition and restored all others partitions. Have you tried that ?

However, I had an old H525n which would not go into download mode or recovery or factory reset using buttons (was most likely a carrier phone which I converted to international) but booted fine using adb commands. In this case, when I restored all partitions using EFS and updated to Marshmallow global, still it WOULD NOT boot into recovery/download mode using key combination as it was somehow locked maybe by the carrier.)

About my H442, dual sim variant i ended up with a terrible mistake.

I nuked (zero command) my tz partition and now I have ended up with a HARD brick myself.

Now then, the device is with a JTAG guy as I have exams and yesterday he called me and told me that he is unable to fix it as NO JTAG guide for that model is available.

Can you shed some light how to recover my device H442 like you did with Lg G3 ? (I know for G2 and G3 guides are available)

My phone is detected by Computer as Qualcomm 9006 / LG Android serial net port but nothing more on the computer. QPST/ QXDM detects it but I am not sure how to flash back the device as no support is available from QPST QFIL etc for LG devices.

The condition of the device. Nothing. No screen no download no recovery no fastboot. Dead.

Only when battery is low, then you try to turn it on, it shows low power notification and that's all I am getting.

But it is detected on PC and it eats up battery on standby so i have to charge it again if the battery is in the device for few hours

Any help be great from you !