If you are stuck because ARB prevents flashing an older KDZ, you have two options:
: The standard "Refurbish" or "Upgrade" modes in LG UP are designed to prevent "cross-flashing" to ensure system stability . How to Resolve It
Understanding LGUP Error 0x5319 The is a common roadblock encountered by LG smartphone enthusiasts when attempting to flash firmware using the LGUP tool. This error code typically translates to: "Not allow to change the device."
The most common fix is ensuring you have the exact firmware meant for your IMEI. Find your (dial *#06# ).