Your beleif in computers is just not mached by reality. I fly a fleet of modern and very well maintained airbuses. I am constantly resetting computers that malfunction. Almost every flight I get one or two spurious ecams. Worst offenders is the datalink and the fuel pumps at the top of descent. The QRH has at least 8 OEBs where the system response has to be modified because it has been found not to be appropriate. Watching the flight director and the autopilot go their separate ways in pitch is quite common. The approach speed calculated by the FMGC and the one calculated by the FAC is more often that not up to 5 kts slower. The list goes on. Computers are just not there and is notthing to do with the processing power.
This is no different to your printer at home, fantastic piece of kit saves me lots of time. Would I trust my life to it though, no. Why? Because every so often it chews up the paper or comes up with error E something. The airbus is no different, great piece of kit but every so often it spits the dummy. I have yet to find a piece of software that has no bugs and the airbus certainly has plenty.