This worked for my 400k model however am sure the same process could be used with KDZ files for the 855 model.
1. Download the 10e KDZ files and the G3 driver from this thread: http://forum.xda-developers.com/show....php?t=2771401
2. Go to this thread and use the method here for how to flash KDZ files: http://forum.xda-developers.com/show....php?t=2432476
3. With that method make sure you choose 'Normal Flash', on the LG Flash Tool. That way you won't lose your settings.
4. Flash 10e KDZ files to your phone.
5. Phone boots and now go to software update and update phone with latest software
6. Use towelroot to root phone again
And you're done!
Takes about 10 minutes.