during the incident flight the bad ADIRU produced 42 data spikes, 40 of which were caught by the computer except the 2 which caused the upset. All these dozens of spikes did not make the computer realize the ADIRU was bad.
It's very important to know if your error correction curcuit is being triggered and take some action. Some decades ago I worked for a company that made "mini computers". These had error correcting memory boards. Some two year old units sent back for repair were discovered to have been incorrectly manufactured. This led to the identification of a whole batch that had been built with one of the memory chips in backwards....and the error correcting circuit had been correcting the consequences for two years.