IF you follow Airbus SOP and verify the position of the aircraft vis-a'-vis the FMGC position (after any kind of alignment),
I wish everyone did this. I am an engineer. Three times in the last two years I have been called out to A320 aircraft because the crew could not align the ADIRUs. When I enter the flight deck the first thing I ask is "present position?".
Then the crew notice that they still have the present position in the FMC from the start of the last leg. No I don't know why but somehow the FMC has not recognised the end of the flight. So enter PPOS and the flashing align lights go out. Trouble is usually the crew have tried to do it themselves first by switching off the ADIRUs and starting again. But if the FMC PPOS is wrong you get the same result.