Frame 4,814............why are you so upset?
Oh the struggles of video editing - one single little frame didn't want to be rendered and exported...........................oh well, i've learned plenty of work arounds over the years - export up to frame 4,813, and then from 4,815....no one should notice .
Investigation takes time, and I've got other stuff to do.
Problem fixed, and now I've sandwiched the two pieces together in a brand new file, and exported them happily.
Andy B