Clips in Project's Timeline do not show orange bar
I have a project with six clips in the opened timeline. 5 of the 6 clips show an orange bar in the browser as they should. One does not. I notice the same thing in various other projects in that event. Most clips show the orange bar when the project is opened as they should but one or two might not. I'm not sure if other events have this issue but a quick check of two other events don't show this issue. This happens with more than one project in that same event. There are a couple of projects that when opened fail to show some of the orange bars as expected. Some clips have the expected orange bar and some do not. What am I missing?
MacBook Pro 15″, macOS 10.14