BYOC Edge Node 502 Bad Gateway during Digital Channel Migration

Migrating digital channels from Zendesk to Genesys Cloud BYOC feels like moving ticket attachments to interaction media, but the Edge node is throwing a 502 Bad Gateway. The Zendesk webhook payload structure seems incompatible with the Genesys Edge routing script. Anyone else hit this mapping issue? The Edge logs show a timeout on the initial handshake. Need a quick fix before the cutover.