SNMPTrapd creates newline characters after 16 bytes which causes issues when Syslog-ng processes the trap(s).
To resolve this issue please override the configuration by placing the following line in the snmptrapd.conf:
[snmp] hexOutputLength 10000
The above command ensures a newline is created after 10000 characters which should be enough to process most traps.
Please feel free to raise this number higher to ensure traps are processed correctly.