Comment by p_l

The incident report on the 2008 case specifically mentions SEU for memory - certain level of EDAC techniques is applied on the whole unit, but one area that was not covered was the possibility of non-catastrophic (in terms of operation) failure of memory module with a bitflip.

An under-appreciated thing is also that the devices in question used to be rebooted pretty often which triggered self-test routines in addition to the run-time tests - something that didn't trigger anything in case of A330 in 2008, but was impactful in risk assessments missing certain things with 787 some years later (and newer A380/A350 recently).