I realized that for some subscriptions, old posts were not scrapped.
Looks like there is some throttling on the API usage. When I debugged , I found out that after 10-15 loops in the get_posts() method from ultima_scraper_api/apis/fansly/classes/user_model.py, the payload returned was empty.
manually going through all the loops (and waiting 1 sec between iterations) allowed me to get to the end of the posts.