This long standing bug now has a fix because gg was able to create the error and then determine that the fix does not create the error. It will be in the end of the month January 31 builds. There is a Debian 9 specific denoisefft.plugin that you can use if you would like to have the fix now. You would have to replace the current one - you could make a copy first of the original. The file to be replaced is attached and its name is:
/usr/lib/cin/plugins/audio/denoisefft.plugin
You would then have to restart Cinelerra. It is safe to do this, but if you are concerned and since you have a workaround, it is your choice.
GG is also looking into the green colored hard edges as they seem to be in places where he does not think they should be. If you prefer not to see the hard edges, you can turn them off under the Window pulldown, option Show Overlays, and click the "Hard Edges" to disable them.
Thanks again for reporting. Phyllis/GG