That's an interesting point, I'm using Chrome now. Previously I always generally used FF.
(But I know I've done the same tab activity in IE and Safari as well).

While this was BA.com, the only reason I had Chrome in use was because there is a unrelated issue (that I've reported, awaiting response) with a bit of the Avios.com functionality in Firefox.
Was advised/asked to use Chrome by the Avios.com team if was doing any bookings, while they investigated the FF issue.

Could be browser, although it is also the first time I've done it since the new booking pages came into operation.