I read this article and tried to convert nDVR videos on 4.4 server.
However, I could not get video crip with correct time and duration I specified with parameters of dvrConverterStartTime, dvrConverterEndTime and dvrConverterDuration.
Regardless of time parameters, I got video crips with whole duration from nDVR.
If you could open a ticket and provide your exact cURL query that you used along with a zip file of your conf/ and logs/ directories. It will be useful if you restart Wowza and reproduce the issue once more such that support is able to get a clean look at the issue.