We noticed this in our logs once! We service a huge amount of traffic, and as part of that, we log what is effectively an enum. We did a summarization of this field once, and noticed that there were a couple of “impossible” values being logged. One of my coworkers realized that the string that actually got logged was exactly one bit off from a valid string, and we came to the conclusion that we were probably seeing cosmic rays in action, either in our service, or in the logging service.