Once a review has been 'Finished' and has a status of 'Awaiting Signature', then the only way to make it open for editing again is to first have it signed by all parties which will set the status to 'Completed'.
Once that is done, you can then click on the context menu, and select 'Edit Review' which will set it back to a 'Planned' status, allowing for further editing.
FAQ: A review has been finished in error, is there a way to edit it again?
Vin Chau