A vague error appears when starting a review request for a document which is locked.
Please, replace a meaningful error message such as "you cannot start a review for a document locked".
This took me (and your supporter) to much time to analyze the problem.
The top ideas with status Quality Backlog are discussed on a regular basis with the design team. These should be minor development, and could include hygiene factors, little things that create a wow effect and ideas that could have a positive effect on a lot of users.