Overcharged by TFL for journey I've taken dozens of times

Hi, I've been overcharged by TFL for a journey I've made many times before. This has happened once before but I've ignored it thinking it was just a one off glitch. However, this time I'm not paying. How can the TFL ticketing system make this type of 'mistake'? Very suspicious. Interestingly, there's no way to claim a refund on the TFL site - they have every option but that. I'm just wondering if this is some sort of scam by TFL knowing that many people won't get round to asking for a refund.