In Mysql, lesson_builder_items (html) is created as type text which is limited to ~21K in UTF-8. With HTML formatting and tables we have hit this limit a few times resulting in the error "Unable to save or update item. Error was: java.sql.BatchUpdateException: Data truncation: Data too long for column 'html' at row 1. "
I'd either convert this to mediumtext (can you just specify this in the hbm.xml?) or do something to handle this error with a better message.