It is very very difficult to diagnose faults on a car from afar but two matters have come to mind. Has the dealer put the car on the diagnostic computer? I know they are remarkably tardy about doing so. Perhaps they have to pay Honda every time they do so.
However, more than once the brakes have been mentioned. Many years ago, in fact nearly 50, when I used to try and fix the monsters for a living, one Saturday morning three young Australian ladies came in with a Morris/Austin J2 caravanette. The brakes were being a problem. In this case, after several applications the brakes were binding and virtually stopping the vehicle. If they stopped for a while all would be well. It took a bit of head scratching and eventually came to the conclusion it was the brake master cylinder. Replaced it and off they went rejoicing. The master cylinder was not allowing the fluid to return to the reservoir. It was a gradual thing as if the return valve was sticking or had dirt in it.
Now I don't know the circumstances but given that the problem doesn't occur immediately is this a consideration? Only BetsyBoo knows when it happens and how much braking she has done before the problem arises the suggestion to touch the wheels near the centres is an excellent idea BUT might I suggest that BetsyBoo feels all the wheels. Be very careful because if they are binding they can get extremely hot. If they are all hot, it would suggest a brake problem. Jolly good luck and I am sorry to say that it would appear the dealer is indulging in the old gender thing. Pat the little woman on the head and send her off with any old excuse. I used to repair so many vehicles on a Saturday morning when motorists had come down to the West Country on holiday after having their cars 'fixed'. In virtually every case it was brakes!!!!!!!! One garage had even put the wheel cylinder rubbers in the wrong way round. Imagine 250 miles of holiday traffic with brakes like that.
