Well ... unless they were caused by stray transient electrical spikes changing the state of the system. These could be a defect but it might also be caused by

Well ... unless they were caused by stray transient electrical spikes changing the state of the system. These could be a defect but it might also be caused by improper input signal conditioning (which would be a defect elsewhere in the system). In either case, we've traditionally called these defects glitches and that lexicon has been broadened to more generally mean "unintended behavior".