WiFi and remote control are broken on a 49sj800v-zb

[Gecko64]

Hello, the wifi of my smart TV is broken since the last update.
The remote control from my phone too when i use an opérational ethernet connection.

Tried : 
Full setting reset
Reboot
Power reset

Observed :
After the power reset and unplugged during at least 10 min, the WiFi networks was at new listed but impossible to connect, it says WiFi network not found.
After a new power off, the searching of wifi networks didn't end without result.
The remote control also lag a lot each 10 seconds and during 3 or 4 seconds.

TV Informations :
Model : 49SJ800V-ZB
Devide Name : [LG] webOS TV SJ800V
Serial Number : 711MAVDM8903
webOS TV Version : 3.9.0-62709 (dreadlocks2-dudhwa)
MAC  Wired : 38:8C:50:F3:2B:5D
MAC Wireless : 7C:1C:4E:A0:E8:C7 
ESN : LGTV20171=11002626448
VSN : 5DBF066A
Widevine : LGTV17CLGE005126094

Question :
Is there a way to downgrade by putting the firmware on a USB Key with a FAT 32 filesystem on to be sure it could be read by the TV ?

Thank you in advance for your help.

 

[Gecko64]

Problem persist, no update, nothing...
I know now what to think about LG...

[Hale]

LG WiFi modules burn like matches from static, AC surges, or unexpected AC loss.

Older model also had bad connectors.

 

It seems, LG uses intentionally weak WiFi-module circuit for phasing out TVs of older non-serviced models. (See Wiki: "Sony timer").

It is very rude, since Philips just uses "grease leaking" remote controls, which become sticky and slimy after 4-5 years, telling you to buy a new TV. On the other hand, Asus uses non-cooled transistor RF switches in their routers, which degrade in 2-4 years, effectively disconnecting the antenna from the transciever...At least LG allows you to watch TV without the magic control.

[lacal]

If no too late, try this :