Some of your Members have a 100% Reject DMARC policy which causes them to be placed in 'held' status because of the DMARC failure. When you check the headers of the message that was rejected you notice two DKIM signatures.
Use a tool like MXToolbox to analyze the incoming message headers. It will indicate issues with DMARC compliance, SPF, and DKIM. Use this information to contact the sender and inform them of the configuration issue.
Aurea offers additional support through our dedicated deliverability experts who, as a paid service, can assist in resolving deliverability issues.