An instance may suffer a crash for any number of reasons. When an instance crashes, their avatar disappears from the sim and a core dump is left where they stood. Some systechs are trained to disentangle a core dump, restoring the crashed instance to a healthy state. Not every kind of crash results in a recoverable core dump, though actual cases of accidental death are exceedingly rare.
Because crashing has such a diverse set of possible causes, it is most useful to interpret each crash as a unique case. Some characters accumulate instability as a result of a reckless approach to instance artistry, while others crash without warning. Others still might crash and be recovered without any lingering symptoms, while yet others suffer life-altering afflictions as a result of their experience.
What is universal is that crashing is a bug; it is a reminder that even those living on the System are subject to the fallibility and impermanence of the System itself. Some instances crash deliberately, not to be confused with quitting, whether to experiment with new techniques for disentangling core dumps or to savor the experience for its own sake or simply out of curiosity.