Hi James, it's tough to know if this is a bug or not.
Has this happened when you're close to a car in front of you, or is there still a bit of a gap between your own cars and one in front?
Sometimes you may be within one second of a car in front, however, when crossing the DRS detection point the car in front may have increased the gap to over one second. This can be true even if the timing view displays the gap shown to the car in front is within one second because the timing view only updates when a sector is completed. Is it possible this is what has happened?