iMovie won’t shut down

Here are some steps that may help.

1. Force quit iMovie.
2. Back up your Mac.
3. Update macOS on your Mac.
4. Update iMovie from the App Store.

If the issue persists, contact Apple Support for further assistance.

Camping Doc wrote:

I regularly make videos from photos with iMovie. I import the photos into the media library via Photos app, and then put them in my time line. No problem. But when I am through for the day, I can’t shut iMovie down. It says that other processes are working and iMovie can’t shut down until those are completed. It also says that the processes are listed in my tool bar. Well, there is nothing in my tool bar, and waiting does not help. I left it running literally all night long and it was still hung up in the morning. The only way I can get out is to force my MacBook Pro to shut down. Then I can do a cold restart and everything is fine. There has got to be a better way to do things than that. And where is that process indicator that iMovie keeps telling me about? I appreciate any help you can give.

If iMovie doesn't behave as you expect it is always a good idea to delete the preferences.

Hold down the Command and Option keys as you launch iMovie until a window appears asking whether you want to delete the preferences.

Select Delete Preferences and iMovie will open as normal although your project may not appear until you navigate to it.

Note that whenever iMovie behaves strangely for no apparent reason it's always a good idea to delete the preferences as a first step.

It won't work every time but it's such a quick procedure that it's always worth trying.