In the custom form that you have open there are currently 100 fields being used - the maximum amount of possible fields is 500

Do they have access to the items they are clicking on?  Could it be a permissions issue?

I think this is the dashboard that you're talking about - I use it and it's very helpful   https://experienceleaguecommunities.adobe.com/t5/workfront-discussions/released-system-admin-maintenance-dashboard/td-p/550997

If you assign a layout template you should be able to do this.   Customize what users see -> Project change to  Customize what users see -> Task

We stick to ProofHQ proofs for everything because it's really confusing to most everyone having both document proofs and PHQ proofs in the same environment.  It's not a problem anymore because everyone is aware, but for a time I wanted to completely disable document proofs.

When I copy the URL and paste it into an incognito browser session I'm able to view the proof without having to login.

Our proofing consists largely of multi-page PDF files

Forgive the suggestion but it seems like you might benefit from not having those exist in 14 different documents based on what you describe

To follow up on this post - through the use of groups and layout templates we can effectively hide any requests that the external users shouldn't see

New Project Report   Add column Project >> Status Update   I suspect a similar function would work for Tasks