Log files should not be closed until their successor is open.
Identifying and debugging this would be much simpler if named ensured that all errors are logged by changing logging such that a log file isn't closed until its successor is open (assuming my guess is correct). This would guarantee that a failure to open gets logged in the previous logfile, which could continue to log. I have verified that the current logging code closes files before opening a successor
The quote is 11 months old - I haven't re-verified the observation in current code as I'm seriously underwater at the moment.