Tried reinstall - still had the same issue. Following the instructions of how to check the bookmarks, I discovered there were several more bookmarks than what I could see on the sequence line. Apparently I incorrectly added some that didn't show up, so now there were bookmarks closer than 2 mins apart.
I couldn't delete the ones I couldn't see, so I deleted the project and started over. The bookmarks to chapter option now works.
Thank you.