Given your experience and you feel that you did touch in, how about you write to Customer Services?
Yes, the advice earlier was to pay - and THEN write in to explain the situation and to ask if there has been any other faults logged with that reader. And if you ask how it could happen, you may then find they refund you as a goodwill gesture, without prejudice etc.
You have nothing to lose but the cost of a stamp, or your time writing an email, giving as much detail as you can so they can investigate. They may or may not do that, but I can't believe you're the only one to have ever had a problem (you clearly aren't, as I had something similar happen) so just give it a shot.
If they can't help, you'll just have to chalk it up to experience and to make sure you always look at the display. It's then you sometimes notice junk on the display, like text stuck from previous touches, and can be on your guard.
I don't think Oyster is broken, but there are clearly some errors. Just as ATMs occasionally go wrong, even if banks don't like to admit it.