I showed our overseas visitors how to use Contactless. They went into Central London where at Bond Street the fire alarms had gone off and everyone was being hustled out and the gates were disabled and open.
It only came to light afterwards that they had a huge charge on their credit card from TfL. It was their only trip of the day. This is the sort of experience that leads to still wanting paper tickets. However is this meant to be sorted out?
That's what the Oyster helpline is for.
Maximum fares arising from incompleted journeys can be automatically resolved in some cases. This was sometimes done for ExCel events where travellers were asked to exit the DLR without touching out to ease congestion.
Whether a fire alarm can be substantially mitigated in this way I don't know. In any case it is still possible to have the journey resolved and any overcharge refunded by emailing or calling customer services, but then of course there's the hassle factor of doing that.
Although balanced against the "hassle" of queuing up for (more expensive) paper tickets every time, rather than just touching in and going.