Fenix 6x Sapphire internal data goes messy after error with Garmin Express Update

Hi friends, I also have a big problem that I can't get my head around:
Last night I connected my Fenix 6x Sapphire to Garmin Express to upgrade the maps.
First GE upgraded to version 7.11.0.0, all ok.
Then it synced with the watch ok.
Then I got an error that I don't have enough space on my laptop to download the topographic maps.
At this point, GE shows me that the watch is no longer connected. I unplugged it and the nightmare began:
Garmin Express no longer sees it, although Windows sees it as a USB device.
All Activities and Sports disappeared from the watch menu, only Multisports remained.
When I try to start an activity, all it states is “Add” as all activities are gone, and then the only sport available to add is Multisport.    Also widgets have disappeared and it no longer wants to connect to the phone. 
Maps can no longer be accessed.
I tried a factory reset / hard reset / master reset, nothing solved the problem.
I tried to reboot the computer, uninstalled GE, deleted all the remains of it and older versions of it in in AppData, etc...
After master reset, the watch cannot connect to Garmin Connect. I suspect that the bluetooh sensor is off that's why, but I cannot access the menu to turn it on.
I have to do a soft reset and then the watch returns to the face I had before the mishap, but it is still non-functional, in the sense that although it connects to Garmin Connect momentarily, it then automatically disconnects, giving me the message:
"Device Not Connected
it looks like your fenix 6x Pro device isn't fully connected. Add your device to make all your features available"
I add the device, and get stuked at sync.
Seems like everytime I manage to link the watch with Garmin Connect, is losing the bluetooh connection. Pressing the Light/power button, I can see that in the menu, the bluetooh connection is disabled. I enable it and redo the links but this things just goes in a loop.
I suspect that something has been miswrited somewhere in the internal memory and I don't know how to rewrite that information. Does anyone know any way to rewrite the firmware without going through garmin programs?
Any help or suggestion is welcome, thank you!
PS> Currently, i have the last stabile firmware, 20.30 on it.