The OP has not stated that the ticket was rejected or adversely commented on the ticket in the posts above. In any of these threads we can only go on what is stated as, as you say, we were not there.
@badcat can you confirm one way or the other if at any time any member of staff raised any concern with the ticket and/or its continuing validity, or if when you asked for a reprint you received any reassurances that it would be fine? Other than LNER's customer services response which I'd agree is absolutely woeful.
To be clear: While I was using the ticket, no one expressed concern about it. Up to and including Day 9, it was scanning. On Day 10, the scanning stopped working around about midday but the ticket inspector took it out and looked at it more closely and gave it back (no comments). After that was when I went in to the ticket office at Manchester Piccadilly. The response to my reprinting request said that it was only possible to get reprints on a season ticket. To be honest, I was surprised at this; I was expecting it to be a least possible. There was no reassurance that it would be OK.
A few hours later, on my way back to Plymouth, I exited the barriers at Taunton. The staff on the gateline tried to scan the ticket with no luck, looked at it. They didn't express concern as such. I can't remember the exact conversation, but it was something like me saying I'm starting to have problems with this ticket, with a response along the lines of I don't think you can get these reprinted, unfortunately.
My original email to LNER was two days after (would have been day 12 of the rover). At that stage, I believed I had few rights, not being fully aware of section 4.8, but I would be damned if I wasn't going to make something of it
A good result for me would be if the systems were changed to allow reprinting as it's a straightforward way to solve what shouldn't be a problem. Yes you need to consider protection from duplicates - surrender old ticket; reissue new bar code and cancel the old one - I can't see ( as a developer) how none of this is doable. I can't see it happening though.