Spam getting through while SA restarts

[geoff . spamassassin3]

I occasionally get a spam leaking through without having been processed 
by SA despite passing the part of my procmail filtering where SA is 
called. These spams are always at the time of scheduled SA restarts so I 
assume they slip through while it is down. SA is called as below, is 
there anything I can do to stop this happening?

Thanks,
Geoff
:0fw: spamassassin.lock
* < 256000
| spamc


# Work around procmail bug: any output on stderr will cause the "F" in 
"From"
# to be dropped.  This will re-add it.
:0
* ^^rom[ ]
{
        LOG="*** Dropped F off From_ header! Fixing up. "

        :0 fhw
        | sed -e '1s/^/F/'
}