I also have this problem. For five years traveled weekly and never once had an issue at any other airport except Heathrow. I asked Border Force and they said to fully bend my passport in half when putting it in. It didn’t make any difference. They said they couldn’t see any chip issue either.
I’ve also gone to the manned desks only to be told I have to try the egates first, which then reject me. It is so frustrating.