The long term metabolite in his system has a pulsating effect. Jeff novistky does a great job explaining the exact science behind this but basically it pulsates and on the drug tests it could show up 20 picograms one day and the next it won’t be there. But it is a long term metabolite that can remain in your body for years and has been happening with low profile fighters as well. The testing from USADA is getting too good because technically he is failing the drug test but it has been ruled multiple times that there’s is no performance enhancing benefits in that small amount.