[syslog-ng] 1.6.11 stops logging on Garbage Collect (Solaris 9)

Our installation of syslog-ng writes to 3 pipes and a dozen files from 2 IP sources. About 2-3 times a week it will stop logging in 1-12 files. The last record in these files will almost always coincide with a Garbage Collect record in /var/log/syslog (which always continues to collect records). Solaris syslog is NOT running. Solaris logadm sends HUP to syslog-ng on any rotate. We tried TCP logging from some systems for a while, but its all UDP now. Important to note, it may not be all files that stop receiving records, or even all the files from a single source. We need reliable logs. How do we begin to debug this issue?