The most likely cause is a DMCA takedown request that removed those URLs from search results, sent before you received Google's "Notice of DMCA removal from Google Search." There can be a significant delay between the removal and the notification.

There's no quick fix, but you're a legitimate partner hosting licensed content, so you're in a position to contest it and get those pages back.

How to find out whether DMCA is the cause

• Set up notifications. Sync your domain with Google Search Console and make sure you have owner permissions. Without this, you won't be notified at all.
• Check Lumen directly. Google sends copies of the complaints it receives to lumendatabase.org, so you can look them up without waiting: https://lumendatabase.org/notices/search?sort_by=date_received+desc&term=YOUR-DOMAIN&term-require-all=true 
• Check the transparency report. Complaints about your domain also appear at https://transparencyreport.google.com/copyright/domains/YOUR-DOMAIN 
• Look at the search results themselves. Search for the affected page by URL or keyword. If a takedown is involved, Google displays a DMCA disclaimer with a direct link to the Lumen report.

How to contest it

Once you've confirmed the cause, file a DMCA Counter Notification. Google's Removals team may contact you for more information afterwards.

Reference: https://stripchat.com/dmca