Cat 8 keystones are shielded to prevent interference from external sources, but they also require proper grounding to avoid interference from within the cable. Wrapping the end connections with copper tape before terminating them is one way to ensure a good ground connection and reduce interference. Using passthrough modular crimping plugs, connecting the RX/TX wires to different pins, or running a speed test on a slow device are not relevant or effective steps to troubleshoot the issue. Reference: CompTIA Network+ N10-008 Certification Study Guide, page 191 CompTIA Network+ N10-008 Cert Guide, Deluxe Edition, page 362 CAT8 RJ45 Keystone Problem : r/HomeNetworking2 How to Terminate Cat8 Shielded Keystone Jacks3