I have an iMovie project which I spent a lot of time cutting and putting in texts. After some hangings on my older Mac I forced quit several times. Now, some clips freeze at preview movie screen, no sound, even though the editing cursor still sweeps over them. The original clips down at event viewer still have sound and play correctly. That means there is no problem with original clips.
I tried deleting from the project the troublesome parts and adding them again from original clips. This did not help. I don't know what's going on.
I guess there is something wrong with project cache, not event cache. But I don't know how to force regenerate project cache.
I deleted "iMovie Movie Cache" and "iMovie Thumbnails" folders under the event folder and let iMovie regenerate them. This fixed 2 clips, but numerous other chunks here and there still have the same problem. In addition, when I turn on "audio waveform", I still see audio waves there.
I also tried exporting the project, the resulting movie has the same problems just as the project.