The thing is, nobody should have been forced to buy a new ticket because of that bug.. given the expiry date was clearly 2018.
The solution isn't to stop using the app, or scrap it, but rather give advice to rail staff to use discretion because it's clearly a mistake.
I wonder what happens if the phone has the wrong time/date, or time zone? I know I've had e-tickets for buses rejected because while my phone had the right time, the ticket machine was out by around ten minutes. As such, it rejected my ticket.
Fortunately the drivers waved me through based on the information shown on the display.
Common sense can solve most issues, and there are more 'options' with a digital card than having left your physical card at home, or losing it. With the app, you can retrieve it (I assume?) from another device.
In theory, staff with connected devices could actually check the railcard themselves - with the railcard owner giving their email address.