(I know that the team is already aware of this issue, but I wanted to post this here for tracking and so other Cantonese learners are aware of the problem and the temporary work around.)
If you attempt to save a Cantonese passage with spaces in it or some rare Chinese characters, the "Save" button will spin indefinitely and the passage won't save. The rare Chinese characters also seem to cause failures to save when used in custom definitions and forum PM's.
The temporary work around is replace these characters with others (i.e. replace all spaces with a dash "-" for example).