Why did iMovie change ALL the clip trimmings?

I just modified my project, uploaded it to Youtube, and a piece of stray audio was over the video (along with the proper audio), so I opened iMovie to find out what's wrong with it.

Well, the issue began before, but I didn't notice it because I just fixed two or three clips, but now ALL the clips are SHIFT.

Not one, not 2, ALL. If there is one fine, I couldn't tell, but EVERY single clip is trimmed at the wrong place.

Time ago happened something similar, because I edited a source video and saved it over, but that time only clips AFTER the edited clip where wrong, and deleting/re-placing the edited video fixed it. I can't find the post in discussions, though. This is not the first time that posts pointing out bugs or unestable behavior are missing, not found, or not indexed in Google.

Now, nothing works. I've used "replace" (drag-drop on top of existing clip), reopened iMovie, duplicated project and working on copies of the original, NOTHING fixes it. Even worse, EVERY time I close and open the project the trimmings for the videos I fixed IS WRONG again.

Last time I found a few odd trimmings (right before to re-publish it to Youtube), the fixes were lost when I reopened the project. Even worse, so it seems the more I try to fix it, THE MORE corrupt it becomes. Now I don't want to touch it, and I'm working on copies of it.

When I found the few oddly trimmed videos, I also found jumps in the same clip, i.e. the same piece of trimmed clip jumps from frame e.g. 340 to 822. Fine editing the transitions, it shows fine when playing left track, fine when playing right track, and the jump when playing the mix.

Here it goes another post to be banned:

*** I LOST TWO 16-hours DAYS IN THIS VIDEO, WITH 80 EDITS, SYNCHRONIZED WITH THE MUSIC ***

I can't believe that replacing a source video damages the whole thing. It's like removing one apple at the bottom of the piramid at the supermarket. That's the worst architecture/behavior I can imagine for an editor.

Thanks Apple. Second time I use iMovie, different Version, second time I have an issue. The same.

Can't iMovie manage more than 1 minute or 10 edits for project?