Suddenly failing on any usage

All of a sudden, one backup server (previously working for some time) is=20
failing on any request to rdiff-backup. For example;

root@safe:~# rdiff-backup --version
Traceback (most recent call last):
 =C2=A0 File "/usr/local/bin/rdiff-backup", line 32, in <module>
 =C2=A0=C2=A0=C2=A0 rdiff_backup.Main.error_check_Main(sys.argv[1:])
 =C2=A0=C2=A0=C2=A0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'rdiff_backup.Main' has no attribute=20
'error_check_Main'
root@safe:~#

The server is running Debian 12.6 with all packages updated. I have=20
tried removing and installing rdiff-backup, but no change.

What could=C2=A0 be wrong?