Keep a dedicated Windows 10 virtual machine or old laptop with SP Flash Tool v4.8.0 and Runtime Trace Mode ready. When all else fails, the traces will guide you home.
You will see lines like:
This usually means the preloader on your device is corrupted or the USB cable is poor. Try a shorter USB 2.0 cable and ensure the battery has at least 30% charge. smart phone flash tool -runtime trace mode- v4.8.0