: A faulty USB cable, a loose port, or the use of a USB 3.0 port (which can sometimes cause timing issues with older SPD drivers) can interrupt the data stream.

Ensure the battery is at least 50% charged. If the voltage drops during the handoff from FDL1 to FDL2, the write process will crash.

: If the device isn't in the correct "Boot Mode," the loader cannot initialize. : Ensure the phone is completely off. Press and hold the Volume Down (or both volume buttons) while plugging in the USB cable. Selective Flashing

is the heavy lifter—it’s responsible for mapping the partitions and preparing the EMMC (storage) to receive the new operating system.

To resolve this, technicians often recommend verifying the exact device model to ensure the .pac firmware file is an identical match, or switching to more modern utilities like spd_dump that provide more verbose logging to pinpoint whether the failure is due to a signature mismatch or a physical connection issue.