@CarbCarbCarbs said:

I think it’s because of the higher amounts of copper.

I don't think so.
HD dark chocolate impact
What are the negative impact of HD black chocolate: Side effects on cardia muscle and focus.
Impact of High Level theobromine?
Answer (Talk with AI - Google)
The cardia muscle (the smooth muscle fibers surrounding the lower esophageal sphincter, or LES) and high-level (HL) theobromine changes the health dynamics entirely. [1]
https%3A%2F%2Fwww.researchgate.net%2Fpublication%2F7901663_The_lower_esophageal_sphincter&ved=0CAEQ1fkOahcKEwiwj4HA9OqUAxUAAAAAHQAAAAAQKw&opi=89978449

When dark chocolate impairs your focus or causes a "wrong" energetic state, high levels of theobromine can trigger a cognitive crash and prolonged brain overstimulation. Concurrently, it causes a direct physical relaxation of the cardia muscle, promoting severe gastrointestinal reflux. [1, 2, 3]

1. Cardia Muscle Dysregulation
   The cardia is the muscular anatomical zone where the esophagus meets the stomach. Dark chocolate negatively impacts it through two distinct mechanisms: [1]
    Sphincter Relaxation: High-dose cocoa stimulates the release of nitric oxide and triggers a direct relaxation response in the smooth cardia muscle fibers. [1]
    Acid Backflow: Once this muscular gateway loses its tone, the lower esophageal sphincter cannot close properly. This permits highly acidic stomach contents to escape upward into the esophagus, causing chemical irritation, chronic heartburn, and acid reflux. [1, 2]

2. High-Level (HL) Theobromine: The Cognitive & Energy Disruption
   Theobromine acts primarily by blocking adenosine receptors (the chemical that signals sleepiness to your brain). While it is structurally similar to caffeine, its half-life is exceptionally long (7 to 12 hours). If your focus or energetic baseline is already misaligned (e.g., you are experiencing fatigue, ADHD-like executive dysfunction, or over-exhaustion), high levels of theobromine can exacerbate these issues: [1, 2, 3, 4, 5]
   PS: Never give a piece of chocolate to a cat, nor to a small dog because it may kill them. Toxic. They haven’t got the right enzyme to get rid of residual molecules.

Explanation
Chocolate contains methylxanthines—specifically theobromine and caffeine. While human enzymes break these compounds down +/ easily, cats and dogs (especially smaller breeds) metabolize them much slower, allowing toxins to build up in their systems. [1, 2]