IMHO, it's a combo or all of: computer/individual OS system literacy, USB port connectivity, home/studio/work network connection, using HX Edit vs. Line 6 updater, being connected (signed-in) to your Line 6 account during update and understanding factory reset, backup options offered in the instructions.
Anyone with a varying degree of attention span (myself included) and parsing details might trip up on any of the above, or all of them at the same time.
Personally, all updates have been worry-free, thanks to great instructions provided and pacing myself during the process, steadying my hands/brain and all...