VSE: Clip audio/video not loading

Dear Forumgoers,

I am not very “computer-savvy”, but am “video editor savvy” and am using Blender as a video editor because of its potential. I am editing a wedding video that is 1:22:57 long.

The problem: from 41:38+04, clips do not register having any audio or video. No waveforms display, the clips play through without sound, and no video appears in the sequence preview.

I thought that it might be a memory issue with my computer, but I have tried deleting all the clips that DO display audio and video, to see whether then the remaining clips would be fixed, and nothing changed. Has anyone experienced this before? I have not been able to find anything similar in forum searches!

Thanks in advance,