The core idea
Yes. Sovereign governments can default, restructure debt or alter payment terms, particularly when borrowing in a currency they cannot freely create or when fiscal and political constraints become severe.
What is happening underneath
Default risk differs greatly across sovereign issuers.
How investors should read it
Even without default, inflation or currency depreciation can reduce the real value of repayment.
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.