> It's unlikely this will have had much impact since most reported cases were only a few days late

I'm not sure if you're being sarcastic or not, but in case you're not, this has meant c.16k people missed from having their contacts traced. That's time-critical. Delays of any number of days are very bad. People will likely die because of this error.

This is safety-critical software. It should be stress tested and have sanity checks. It should be impossible for this to happen.

For something like this system, part of a track and trace system costing billions, to fail because of a file size error is just unbelievable.