doc1gen trace files not getting flushed in server mode

Problem with doc1gen trace files

Problem description:
Customer has some problems with trace files when trying to debug Generate.
The trace files are not always properly flushed before closing them (or are not closed properly), so some content can be missing. It seems the content is flushed when the next file is opened, and not before that.

The trace file is not flushed properly when running in server mode. The last several kilobytes appear to remain buffered until the next file handle is opened. When the next file is opened, the previous file gets written to the end.