subnet seems selected on source address not gateway address

[Peter Grandi]

>> [ ... multihomed relay forwards with a source address that is
>> not the gateway address ... ]

>> Some said that this happens when 'shared-network {}' is used,
>> for example, and some other seem to say that the source IP
>> address is always used; the sources seem to prefer the
>> 'GIADDR':

> Are you using shared-network? If you are, then that is a
> misconfiguration.

Of course, that's why I mentioned it. I wondered if there are
other hints and known mishaps to look for. But I don't know yet
if GIADDR is used in the configuration or now, see below.

> You haven't shown your dhcpd.conf, so we can't say for sure.

Regrettably that server is managed by someone else and I haven't
got a copy of the configuration yet.

Since the someone else are very busy and I really depend on them
to get this fixed, I am trying to collect hints and to list
things ofr him to look at to help him, thus the guesswork nature
of my query, sorry about that, please bear with me.