The software crashes when there are stability problems, codec issues or file errors. I have tested the application and tried to convert an MP4 file, and then the software crashed as well. To fix it, I had to close all the background programs and launch it with Administrator access. Selected a PRESET mode from the conversion window and launched the process. Everything went smoothly, and the video was converted based on my preset.
As a precaution measure, create a copy of the original file and convert that, just in case it gets broken.