Just as you know, there are several reasons may cause this error occurs, such as an old version iTunes, an upgraded iPhone, a hardware issue and so on. To fix iPhone stuck in recovery mode, just try the following steps:

1. Update your iPhone, which is the most basic way to figure out error 1669
2. Update your iTunes, ensure that your iTunes is the latest version
3. Restore iPhone with DFU mode, which can help your phone detect to iTunes without activating the boot loader
4. Recover using iOS system recovery, which can get your iPhone out of recovery mode without losing any data

Hope this can do a favor for you.