Data Action webhook timeout on ServiceNow ticket creation for long chat transcripts

Trying to make sense of why the ServiceNow Data Action is consistently dropping the tail end of JSON payloads when triggered by the messaging:conversation:wrapup event for extended chat sessions. Environment is GC EU-West (v2023.10) integrating with ServiceNow Madrid 13.1. The payload exceeds 50KB and hits a 502 Bad Gateway. Is there a documented payload size limit for outbound Data Action webhooks, or is this a timeout configuration issue on the ServiceNow side?