no GPS reception any more

Hi, today all a sudden my Fenix5Xplus did not find any satellites any more. so NO GPS,GLONASS,Galileo...

I started with a "hold power button 10 seconds" reset
then I used the software option reset
then I used the "hard reset" holding top right and lower right button until first beep, then release ups and wait for second beep .....
tried installing the latest BEAT 4.74 (with all files in in the remote SW folder, even the ones which were already uplevel)
finally I deleted all files out of the filesystem (beside of the APPS folder and the copyright txt which were write protected)
.
no success
.
I started the RMA process, but while waiting for Garmin (weekend just started :() any hints or further recommendations are welcome
.
is there a possibility to "downgrade" GPS to 220 ? (it is currently at 224)