Why my NFC passport didn't work at Heathrow's eGates (opens in new tab)

I travel a fair bit. My passport is usually quickly scanned and I can enter or leave a country without delay. But every time I use the eGates at Heathrow Airport to get back in to the UK, my passport is rejected and I'm told to seek assistance from Border Force. Today, I think I discovered why! The border guards are usually polite and tell me there's nothing wrong with my passport (not that they …