OK, the followng is work in progress, problems I've encountered, possible solutions: Its not a definitive guide, as I haven't quite worked out the exact step-by-step proess I applied.
I do now have it working properly with 1.54 including RAID 1, and am able to force a re-update (1.54) on top in debug mode (both reformatting and not reformatting), which is installed without errors, shows future updates will (in theory) work - this is a good indication that the firmware has being applied correctly.
I don't think the 'firmware' is at fault as such, I think the refurbished models from ebuyer (well the one I received) have an incorrect TFTP Version installed, which is incompatible with 1.54, if upgraded directly, especially if you select Debug mode with all options selected ie. select reformat. or remove existing disks and insert two blank Samsung 2TB Drives. (Many people buy these to replace the existing disks with larger)
In the past I've thought the firmware update had worked - only to start storing data -- then find future updates could not be applied due to 'disk not recognised' errors, ie. there was a problem with the disk layout/structure preventing an further update. I've only really started having 'bricking' problem since 1.54, though we do have a working one that can't be updated because of the 'disk not recognised' error, running 1.41 firmware, but in itself data is intact and working correctly.
Quite experienced with Buffalo Products (I DON'T WORK FOR BUFFALO), and bought another via ebuyer 2 weeks ago- one of the refurbished units. Firmware 1.54 is extremely 'iffy' upgrading, not sure but missing out interim upgrades such as 1.33, 1.41, 143 etc may be the problem. These can be downloaded by replacing the existing number 1.54 in the download link with 1.41 etc.
If you don't replace the stock TFTP, 1.54 definitely fails (consistently) each time if you attempt it using Debug mode and have reformatting selected/all options selected, which is the normal way I attempt upgrades if dealing with blank/new disks. (This then requires the use of TFTP to recover the unit)
If you do manage to install 1.54, check that you can install future updates by using Debug Mode to force a further 1.54 update over the top, as this often fails. Getting this working has taken a good few attempts.
There seems to me to be a mismatch between the installed older TFTP and the latest firmware, applying the correct TFTP solves the problem. I think its due to Buffalo adding support for larger than 2TB disks - the disk /format stucture/layout has changed.
Its seems the newer versions of TFTP are plug 'n' play , ie. you insert two unformatted hard disks and the drive will enter EM Mode, rather than produce an Error with E06 (6 flashing lights), which then requires the TFTP process to be used to recover to EM Mode..
Solution:
Buffalo need to make available the latest version of TFTP (the buffalo FTP Site only has 1.33), which matches the current firmware. There are ones dotted around the internet, 1.41 Kirkwood, 1.43, 1.53. I think I had sucess with 1.41 Kirkwood.
I found it better to start with two completely wiped Hard Disks at each attempt of restoration (using Paragon Hard Disk Manager connected to an external desktop). Also found restoring using the installed 500GB drives first, before attempting to upgrade disks to Samsung 2TB disks, if that is your plan.
There is definitely a problem upgrading these LX Series models directly to firmware 1.54 from whatever older stock version they are running when bought , the one received was Version 1.24.
There is also a design problem in that metal tabs which separate the drives are easily damaged in transit, and the plastic clips can break off. This is more of a problem with the heavier/larger drives due to a lack of packing material between the drives.
The one received hard drive 1 jammed diagonally, on receipt, but was able to remove the disk with a fair bit of force (no tools used) and then use a screwdriver to twist the drive separating tabs back into position.
Will try and replicate how I managed to get this installed, as I've a second unit to attempt with the drive mismatch error but data has to be backed up elsewhere beforehand. ie. the exact version of TFTP I used from ones found on the internet. Have a feeling it was TFTP Boot Recovery 1.41 Kirkwood, but I found several 1.33 (from buffalo site), 1.41, 143, 153, and one for the V-Series of Linkstaton.
Would prefer Buffalo make the latest version available, as 1.33 doesn't work when upgrading to 1.54, and using downloaded ones off the internet is not good practice if you don't know the files source.
When Bricking occurred I also had Comodo Installed, with all options disabled though. For subsquente updates I then used a different XP laptop/machine without any Antivirus software / Firewall installed, so Comodo may also be an issue. If you do use Comodo, worth using a machine wihout it installed.