Editing a nested clip sometimes results in clips outside the nest disappearing from the timeline

I'm working on a project with multiple video clips in the timeline. In order to apply noise reduction evenly to all the clips, I nested the clips and used a 3rd-party product from within Premiere called Neat and applied noise reduction to the nest. Worked great! Then I added titles to the timeline above the nest (titles did not need noise reduction). Again, worked great.

Problem: At one point I opened the nested clips (by double-clicking) to edit one of the clips in the nest, then I saved the project before closing the nest. When I re-opened the project, the nested clips were on the timeline, opened for editing as I left them, but when I closed the nest the title clips that were outside the nest, as was the audio tracks, were gone, nowhere to be found. Where did they go? How do I get them back?

I tried to reproduce the problem for screenshots here, but now I can't reproduce it. Maybe it was just a fleeting glitch? From now on I'll just try to remember to close opened nests before closing a project. Thanks. Adobe Premiere Pro 23.1, Windows 11