I've literally registered on this forum to tell you that you are not alone. I thought I was going mad - AW4, probably red light at tube gates 80% of the time and then works at the second attempt. It's so frustrating and does annoy people queuing.
I actually work in digital and mobile payments and have done so for years, so by coincidence was experimenting a month ago with different devices to see what the success rate, as on AW1 I used to also get "Card Unavailable" about once a week.
- Fitbit - Fitbit Pay works flawlessly at any TfL Barrier, 100% success for a week even from an inch or two away
- Garmin - Garmin Pay works flawlessly also, 100% success for a week although anecdotally not as quick at Fitbit
- AW1 - ApplePay generally works flawlessly but slower to read and has "card unavailable" issues once a week
- AW4 - ApplePay fails first time 80% of the time (red light) often with watch showing "Done". Works second time
Have seen the comment that says AW4 NFC is lower power and needs to be closer or touching the reader - my instinct only, but if you've pre-armed ApplePay (i.e. before reaching barrier) am pretty sure reader flashes red
before you can touch.
In other words the reader detects something from an inch or two away before you've had a chance to touch but then decides it doesn't like it or can't accept it. There is no way round this issue from my experience. Has Apple issued any feedback?