Next.js Dynamic Metadata Fix

I need this solved today. On my Next.js 13 App Router site the route /accumulators/[date]/[slug] fetches content and metadata directly from Supabase on every request, yet the page title, meta description and Open Graph / Twitter tags sometimes revert to the default template. The failure appears only on certain slugs, not site-wide, so crawlers are getting inconsistent data.

Your task is to dig into my generateMetadata logic, identify why the App Router occasionally returns undefined or cached values, and deliver a fix that guarantees correct SSR output for every slug. The stack is Next.js (TypeScript) + Supabase on Vercel—no WordPress, no plugins.

Within 24 hours I expect:
• a working code update (single PR or patch) that reliably serves dynamic title, description and social tags for all routes
• validation proofs from Facebook Sharing Debugger and Twitter Card Validator
• a brief technical note on the root cause and the change applied

Start your proposal with ACCA-SEO and, in one sentence, explain why generateMetadata may misbehave on dynamic routes so I know you read the brief.