Glitch happens if i uncheck weapon animation while stow. At some point those weapons simply disappear, even if i am currently in combat. There are two examples:
Today at fractals, Wall of the Mists should be in off-hand. But it is invisible.
And today during Ogre Wars, Vision of the Mists doesn't show itself.
I cannot determine when it happens. Possibly low graphics is the reason. But even so, when i have show weapon animation while stow, no glitch happens. It is possile that other weapons of this skin-family have that glitch. But so far it didn't happen with Whisperblade.
It is really sad, right now i've decided to have stow weapons checked to prevent that glitch. Hidden illusionary weapons while stow really fits well with mesmer