Synaptic error message -- indicates repository malfunction

[Richard Owlett <rowlett@cloud85.net>]

I just attempted to install kde-baseapps-bin via Synaptic.
I received a message stating
> W: Failed to fetch http://security.debian.org/debian-security/pool/updates/main/p/poppler/libpoppler-qt5-1_0.48.0-2+deb9u1_i386.deb
>   404  Not Found [*****]


***** is an IP address, deleted as I didn't know whose it was
Known problem?
Where should it be reported?