Have seen this in previous versions as well. Looks like an issue of focus.
Reading a resource, if I mark it for highlighting, it doesn't always work unless I first click the resource. For instance:
- Open a resource
- Open another resource and do something in it (I've got a book and a Bible open; I've been clicking references in the book then going to the Bible and from there adding to passage list (wanting more or less verses than mentioned in the book))
- Select a section of the first book; don't click in it except to select a section
- Hit cmd-k
- Wince as the application mocks you with an error chirp
- Click the book
- Try the highlight again
