Upgrade the latest firmware last night using USB cable (to fix the sub-trim level bug). One "device restart" but successful second time attempt, I just used main power switch backpanel on/off during the process without actually unplugging the power cord. Since I didn't deleted the first firmware file, I have two version of firmware files in my laptop. BTW, this firmware upgrade did fix the sub-trim level bug for me. Even if there is some potential firmware upgrade problems, I will continue to upgrade the firmware as they become available.