What I still don’t understand is just because the FDPS couldn’t deal with 1 FPL out of the thousands in the system at that time, it decided that forcing the whole system to revert to manual mode is preferable to just displaying the potentially incorrect flight data to ATCOs for that 1 flight. Bearing in mind that ATCOs safely deal with dodgy flight plans or flights with no FPL tactically on a daly basis anyway.