Or, if it is a system based on many components that can be independantly updated, some bugs may be introduced because a mismatch caused one variable to corrupt

Or, if it is a system based on many components that can be independantly updated, some bugs may be introduced because a mismatch caused one variable to corrupt and then that one just keeps being propagated to newer versions until it triggers a bug because you assumed it can never have that specific value. Which, it actually can't in the current state, but only because of the system itself changin, or evolving, over time.