Yep. I had a similar problem when working for ASDA Home Shopping in the summer. We had a time slot for each delivery to a customer. It was perfectly OK to deliver late, due to 'Operational Difficulties' or 'Computer Failure' etc.
However, we were only allowed to deliver 20 minutes before the timeslot. I got back to the depot on one occasion and was given a telling-off because I'd made a delivery 21 minutes before the alloted time. Apparently, this would incur penalty points against the management and they were in danger of falling short of their KPI (Key Performance Indictator) and therefore their monthly bonus payment was it risk.
I made a point of making a few more early deliveries before leaving them.