False positives?

Ive heard from several sources claims 7-hydroxymitragynine or kratom in general will cause false positives for fetty.. well I am going to test this theory with 5 people to start. 6 including me. I did one test as a base control. The result was a faint pass but a clear pass. The photo doesn't do reality justice, but it does show the line.

warning** Last Photo is photo of sample.