Rules in local.cf are not read?

Hi all,

I'm using MailScanner with SpamAssassin, and I'm using the "Cache SpamAssassin Results = yes" option.
Since I've enabled this option, I'm seeing that some spam messages pass through, although the subject or body match one or more own-written rules in my local.cf file.
If I look at the header of these messages, they have:

X-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, timed out)

If I save the message and try "spamassassin -D < mymessage" it is correctly detected as spam, also against the rules in local.cf file.
I know that SpamAssassin sometimes times out on network checks, but aren't the rules in the local.cf file read anyway?

Thanks in advance for your help.

Simone.