While reviewing references, I am shown a HTTP 500 error.

If you are reviewing references and are shown This page isn't working HTTP ERROR 500 message on-screen, there may be several reasons for this occurrence. 

1. Faulty or incomplete Form configuration(s) in the Workflow - check any Forms containing Subforms. Additionally, make sure all Subforms are linked to a question in a parent Form. 
   
   
2. Incorrect Filter configuration(s) in the Workflow - on the Manage Levels screen, ensure all your Filters are correctly set up for each Level and/or Form. This error may also occur if a question, Form, or Label is deleted or a reference is quarantined, but an existing Filter is calling that reference, Label, Form, or question.