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

[Kim Cary]

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?