Outbound Campaign API 429 Throttling in Multi-Tenant AppFoundry

Trying to understand the rate limit enforcement for POST /api/v2/outbound/campaigns within a multi-tenant AppFoundry deployment. We are hitting 429 Too Many Requests consistently when syncing campaign lists across multiple orgs using the same OAuth client, despite respecting the documented 60 requests per minute cap. Is there a per-client global quota that supersedes the per-org limits?