Hi, it's almost since the beginning of December that I'm facing this problem. Whatever sim card i put on slot 1, it randomly stops working. Sometimes all of a sudden, sometimes when I deactivate the airplane mode in the morning.
There's a 50/50 chance I'm able to recover it, otherwise I have to wait until it goes back to work again. It could take hours or even days. Living in a foreign country it's a must have (for me) to have both sims working all time.
I have already tried all the easy steps you mentioned to the other guys: clear cache, restart, swap sim, use only slot 1, reset the network settings -> no success at all.
I then tried to upgrade to Android 12 hoping it was just a software bug: nothing. Then I tried to reset the phone: nothing.
I then started looking at the logcat (focusing on the errors) to see if some info are useful for you (which you can look at the pics attached)
Now, I bought the smartphone in my birth country but now i'm living in another one (Still in Europe) for work reason. How can I get support without staying with no smartphone, which nowadays is a vital device for the everyday life? Is this a software bug that could be solved with the next patch?
