Xperia X Compact - Device is Corrupted

[X-Compact-User]

Hi
Yesterday suddenly my phone restarted, and an error message occured: Your device is corrupted and cannot be trusted.. something like that.
I was able to restart it, but it can't find the SIM-Card anymore. Furthermore messages keep popping up from several programs eg. Google Play has stopped, Photos has stopped....
I made a factory reset, still the same things (corrupt, ... has stopped)
Next i tried the software repair tool from the companion app. Error message came: can not complete reset. Try again (something like that, was german). Thing is, I can not try again, because I can not do anything on the phone anymore. It's detected by the computer, but companion app wants me to unlock the screen, which I can't do.
Don't know if it's just due to it's age (4 years in use now)?
Is there any hope for my phone, or should I just get a new one?

[Lord_viridis]

That is the warning message once a devices bootloader has been unlocked and a new bootloader installed?

Did you previously root the device?