I had to delete the SEO app that I’ve used for over three years and it went away. 
Topic summary
Issue: Google Merchant Center flagging products with a critical “duplicate Brand” error after theme updates or when using certain apps.
Root Cause: Multiple sources generating JSON-LD structured data with duplicate "@type": "Brand" fields—typically from both the Shopify theme and third-party SEO/review apps running simultaneously.
Apps Identified as Culprits:
- SEO Manager ($20/month)
- SeoAnt
- Strong SEO (now offers duplicate prevention feature)
- Judge.me (review app)
- Schema Plus
Solutions Found:
Quick Fix: Uninstalling the conflicting SEO or review app immediately resolved the error for most users.
Judge.me Specific: Disable “Add JSON-LD snippets” under Marketing and Social > Google and SEO > SEO Rich Snippets, then revalidate in Google Search Console.
Alternative: Keep one JSON-LD source (preferably the SEO app if it includes priceValidUntil and other rich snippet fields) and remove duplicate code from the theme.
Edge Case: One user found a “featured product” widget on product pages caused duplication.
Status: Multiple confirmed solutions; Strong SEO now provides built-in duplicate prevention. Users should audit which apps/theme elements generate structured data and ensure only one source outputs Brand fields.