All the places selling it are probably putting different things into it, and it could be anything from banned cathinones to larocaine to some entirely novel research chemical.
The solution is to not buy from any vendor who sells "branded" legal high products without providing a credible chemical name, and any vendor who is evasive when asked about the contents of their products.
Recall the investigation of "nrg-1" after the mephedrone ban, which found that most of the many batches were actually banned cathinones (a chinese wholesaler may have been selling excess mephedrone as naphyrone), cut MDPV, or completely inert.