Kat wrote:
Any LU ticket office should exchange a paper ticket that is not
working
for one that will open the gates.

That's not what I was told when I had a similar problem. Apparently it
costs too much to make a new ticket and isn't worth it for them if the
ticket is valid for less than another week. I did manage to discover
how easy it was to get in and out of stations without showing a ticket
though