I've noticed as playing as an assassin sometimes my smoke bomb will be ready and i'll try to use it (standing still) and it won't work, i just end up standing there like an idiot, ending up dying because my smoke bomb never went off, also happens if im alone and not in combat sometimes. I didn't see this in the list of known issues.
I think this one is lag related, a lot of the skills will misfire randomly. Does it consume the skill's charge or just not recognize the button press?
That might just be lag but there's a chance you were airborne or something (maybe someone knocked you back), although that certainly wouldn't explain the frequency of the event. If you were hit by any sniper traps or the sniper's bot then you might've needed to recharge, but I take it you would've noticed the meter filling.
I've had it delayed (greatly) and also just simply not gone off. Both have taken place in laggy games though, never had the problem in a game that was otherwise running smoothly.