Harmonious Mantras trait bug
I was just on my mesmer today. I charged my mantras with 3 stacks and I was killing mobs without using a stack of my mantras or using a waypoint. About 5 minutes in, I lost 1 stack on each of my mantras (dropping to 2 stacks). I’m sure this is a bug. I hope this information will help to find a solution. Thank you. 
(edited by Emmett.9210)
It also happens when going downed. When you rally you’ll lose a charge if you were at 3. This bug has been around for a while, just like the bug with clones not having any offhand weapons and trident clones having no weapons. Still waiting for all of these to be fixed. (clone bug has been around since feature pack2)
It also happens if you use a tonic that transforms you.
You don’t win friends with Salad.