Bugs. There are many computer professionals on this forum. Ask anyone of us if there exists a computer program without bugs. Axe me. How many computer programs run a modern Boeing 777 jet? How many lines of code? How many bugs do they have? Hundreds or thousands? At least. Think about it next time you board a modern jet airplane. Think about blue screens - Microsoft doesn’t have a monopoly on them. (Yet.) Program bugs could of diverted this aircraft to La la land, I think.
I’m a software engineer and a pilot. I also have a masters degree in aviation safety.
Yes, all software has bugs and unplanned for / untested “edge cases”. However this particular aircraft doesn’t need the computer to fly and it can be switched off.
The transponder is an isolated piece of equipment on the 777. It isn’t linked to any other digital system in cockpit. So a flight computer going bad couldn’t impact the transponder in anyway.
This thing has 7500 written all over it.