When coming in to platform 9 at Reading in a HST there is an AWS that doesn't notify you in the cab but applies your emergency brakes
Ah, that's what it was I had! I posted about it the other day. Also similar things happen on turning around during the Christmas closures scenario. Keeps triggering in cab without an alarm forcing the brakes on every few minutes.
I've experienced the same. I've tried going into that platform at very low speeds and it still triggers a stop. I end up turning of TPWS before arriving at Reading... Even though it ruins the simulation for me.
You apparently can avoid this by pressing the [Brake Override] button (it's above the windscreen, on the left), shortly before reaching the platform. Not realistic, but not as immersion- breaking as disabling the safety systems.