insert_iptables() in /usr/lib/pgl/pglcmd.lib has the following in the case... FORWARD) section:
which is just plain wrong as it results in the attempted command:
iptables -I pgl_fwd -m iprange '--src-range --dst-range' <start>-<end> -j RETURN
for configured values of <start> and <end>.
Basically the whole handling of forwarding options needs rethinking and recoding.
For now I've changed the ALLOW_FILES bit for FORWARD to have:
as that suits my purposes. The code likely wants entirely changing to put in separate source and destination commands though.