There are times when new developments overtake or cross over each other. The writer remembers one occasion when a newly released function in the 9020 was brought in for an operational trial under close observation in quiet hours and it didn’t work as expected with aircraft above FL350 because when the original code was written civil airlines didn’t fly that high. I believe the flight management software in the first Boeing 757s had similar problems as it was conceived originally as a short haul aircraft?
Below is a link to a letter from the ICAO Euromed regional office in Paris alerting ATC to the fact that Reduced Vertical Separation Minima were to be introduced but that TCAS would at that time still issue an alert if vertical separation was less than 2000 feet even though 1000 feet was about to become the new vertical separation. It describe the anticipated problem and potential scenarios, identifies the training issues and even has a quiz for controllers.