Program crash during editing or exporting may be caused by high system load, thus it's recommended to close other programs while working in Editor.
You can also generally reduce system load by disabling certain options in Editor.
Launch Movavi Video Editor.
Select Preferences from Settings menu.
Disable Intel hardware acceleration and NVENC acceleration (if available) and click ok.
Relaunch the program and try saving your project again.
Movavi Video Editor
Movavi Video Editor
Movavi Video Editor 14.2.0 plus