Adding a title in iMovie 10 causes it to freeze
When I try to add a title in iMovie 10.1.8 to a short video clip, iMovie becomes unresponsive for at least minutes. I've tried dragging a title to the timeline, and positioning the playhead at the desired location and double-click the title. I'm looking at the iMovie Help narrative for adding a title.
What am I doing wrong? How can one add a title without iMovie freezing up?
Running High Sierra on a 2017 iMac.
iMac, macOS Sierra (10.12.4), 16 GB RAM