I've been experiencing this issue with VideoPad for quite a while now. Sometimes it happens that, at the point where the timeline has a clip edge, the whole rest of the exported video turns out to be a frozen frame that's either a black screen, or the frame that's represented in the clip edge. It's easy for me to notice when this is happening because of VideoPad exporting the video abnormally fast, and the file size turns out smaller than expected.
I've once had this happen when at an edge, clip B was sped up; other times because there was a snapshot between two clips that are both a few hours long, and now I'm experiencing this when the in and out points are altered.
It's an exporting glitch that just with miraculous workarounds it's able to get fixed, but it's such a time waster because I'm working with really long videos, and they take forever to export. I'm using v6.10, and it exports the frozen frame in the place of where the real video content should be. And also, there's no audio at all... actually, scratch that. There had been several times where the part with the frozen frame had no audio, but every one in a while it DOES have audio.
I really hope this gets fixed in a later version...