Cursor pagination limits on analytics/conversations/details/query

Could someone explain the behavior of cursor pagination on /api/v2/analytics/conversations/details/query? I’m building a ServiceNow script that pulls conversation details. The first request with "size": 1000 returns data and a nextPageLink. When I append that cursor to the next request, I get a 403 Forbidden. Is the endpoint strictly enforcing a smaller page size or is my OAuth token expiring mid-flow? The nextPageLink seems valid but fails consistently after the first hop.