Hello! Based on the information you provided, it seems that your POCO X3 Pro is experiencing issues with the System UI crashing and rebooting. It's good to hear that you've already tried to address the issue by having the device repaired and downgrading the software.
There are several possible reasons why your device is experiencing these issues. It could be due to a software glitch, a hardware problem, or a combination of both. Here are some steps you can take to further troubleshoot the issue:
1. Check for software updates - make sure that your device is running the latest software version available. You can check for updates by going to Settings > About phone > System update.
2. Clear cache and data - clearing the cache and data of the System UI can help resolve issues. Go to Settings > Apps > System UI > Storage > Clear cache and Clear data.
3. Boot into safe mode - this will run the device with only the pre-installed apps, which can help you determine if a third-party app is causing the issue. To boot into safe mode: Press and hold the power button > Touch and hold Power off > Tap OK when Reboot to safe mode appears.
4. Factory reset - if all else fails, you may need to perform a factory reset to bring your device back to its original settings. Make sure to back up your data first before doing so.
If the issue persists after trying these steps, it may be best to bring your device to an authorized service center for further assessment and repair.
