This sounds like a co-ordinated slot problem - the runway slot held is, say 0800, and because of the generous sched and light winds the aircraft turns up STA -40, the slot committee review this and summarise that the operator is not adhering to it's slot.
Potentially very serious and after series of warnings, operators will have the slot revoked - worst case they can be banned from operating to the airport.
Always the problem with operating padded schedules. ACL (Airport Co-ordination lLd) are the people to ask)