syslog – Error processing log message

We are using syslog-ng version 3.5.6 (Cent OS Linux) and while receiving the logs via port 514, we observed below error message:

Error processing log message : followed by the message

Below is the current configuration :

source s_external {
syslog(
transport(“udp”)
port(514)
so-rcvbuf(2024000)
);

destination udpdata { file(“/destination/${FULLHOST}/udpdata.log” template(“${MESSAGE}n”) create_dirs(yes) ); };

log { source(s_external); destination(udpdata); };

Can someone help me why this error message is seen in the logs?

Regards,
BK