Gecko64

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

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.