SEO expert for site-wide Google drop on a large Next.js site (diagnosis first)

We run a content site in the streaming/entertainment space, built on Next.js. In August our Google search traffic dropped sharply across the whole site and hasn't come back. Bing still sends traffic normally. We've already worked through the standard technical checks (crawling, robots.txt, sitemaps, canonicals, manual actions, site speed). Those are done, and we're looking for someone who can diagnose a site-wide quality/trust problem, not run a generic audit.

Phase 1 (fixed price): review our Search Console (read-only access) and the site. Then give us a written diagnosis and a prioritised recovery plan, with impact, effort and a realistic timeline.
Phase 2 (optional, quoted separately): help carry out the plan.

Must have: proven recoveries from site-wide Google drops (ideally large or template-based sites); experience with JavaScript/Next.js sites; white-hat only. No PBNs, paid links or bulk link-building, and no ranking guarantees.

To apply, answer:
1. Describe a site-wide recovery you led: what was wrong, what you changed, how long it took.
2. How do you tell a site-wide quality judgement apart from a technical problem?
3. What would you ask us for first, and why?

Full details and the site link are shared with shortlisted applicants under NDA.