DIAGNOSIS The most common culprit is the Velop's "CA" (Channel Availability) or DFS radar detection feature. It's choosing a "clean" but slower channel to avoid interference, or it's stuck on a congested channel.
FIX Log into the web interface at linksyssmartwifi.com. Go to Wi-Fi Settings > Manual. Change the 5GHz Channel Width to "80MHz" (not 20/40/80 or 160MHz). Change the 5GHz Channel to a fixed number like 36, 40, 44, or 48 (the non-DFS channels). Apply settings. Retest speed. This forces it onto a standard, fast channel.
IF THAT DIDN'T WORK Check for an active "Node Steering" or "Client Steering" feature in the app under Wi-Fi Settings. Sometimes these features, while meant to help, can throttle connections during handoffs. Try turning them off temporarily to test.
HEADS UP The Velop, like all mesh systems, has inherent overhead. Don't expect to hit your full 1Gbps plan speed over wireless; 500-700Mbps on a close 5GHz connection is typical and good.