Below is what from Apple Support Team to fix Error 1611:
1. Use the original USB cable. If you don't have it, try a different Apple USB cable.
2. Switch to a different USB port on your computer. Don't plug into your keyboard.
3. Switch to a USB port on a different computer.
4. If you still see the error, check for other USB issues, check your third-party security software, then check your hardware.
Besides, it's practical to try a system repair tool for iPhone, like Fippox, Joyoshare UltFix, Repair, etc. No data loss even.