I just stumbled upon this scientific paper from 2018. It references a Dutch study where 46 canna oil samples from patiens were analyzed. It's shocking how the labels deviate from the actual concentrations.
Here's the link to the paper: https://karger.com/mca/article-pdf/1/1/65/3068377/000489287.pdf
And the other related issues: https://karger.com/mca/issue/browse-by-year