Facing persistent Schema Markup validation errors with nested JSON-LD, is it a parsing issue?

hey, been banging my head against this. trying to implement some complex Schema Markup for product listings but google's rich results test keeps throwing a weird error. i'm nesting multiple types and it seems to break when i go past two levels deep.

{
  "@context": "http://schema.org",
  "@type": "Product",
  "name": "SaaS Product X",
  "offers": {
    "@type": "Offer",
    "priceCurrency": "USD",
    "price": "99.00",
    "availability": "http://schema.org/InStock"
  },
  "review": { // This is where the issue usually starts
    "@type": "Review",
    "reviewRating": {
      "@type": "Rating",
      "ratingValue": "4.5"
    },
    "author": {
      "@type": "Person",
      "name": "Jane Doe"
    }
  }
}
// Simulated Error: "Missing field 'itemReviewed' in 'review' object at path $.review"

does anyone have experience with deeply nested JSON-LD and how to troubleshoot these validation fails effectively?