The core idea
Redenomination risk is the possibility that a debt obligation is converted into a different currency, often in the context of stress within a currency union or a change in monetary regime.
What is happening underneath
Investors may demand a spread when they believe the replacement currency could be worth less than the original one.
How investors should read it
It is distinct from conventional default risk even though the two can interact.
The same market move can carry different information depending on which maturity, issuer and risk premium is changing. Read the question together with the underlying concepts rather than treating one price move as a universal signal.