Editing a video creates a new file where the video plays for 3-5 seconds, then freezes, but audio continues.

If I want to edit a recording and select the portion I want to cut out, it will save the file size around 24 MB. When I go to play the edited video, it plays for about 3-5 seconds of video, the video will freeze, and only audio continues for the rest of the file (it has the complete audio). This is less of a problem if I'm editing the end of a video, as the credits freeze and the audio keeps playing, making me less frustrated, but I don't like it. 

Why can't it just cut what you select and save it as a full file without this issue? Any fixes? Any way to cut the parts out without the video freezing?