There are several problems caused by circular certificate chains:
# Kleopatra crashes on startup if there are X.509 certificates with a circular certificate chain in the key store.
# Kleopatra hangs when trying to view the trust chain details of a certificate that's part of a circular chain.
See {rGc9343bec83e2c2a14b564b8a13998806eab1ae9f} for test certificates with circular certificate chain.