Ok, figured it out. I am there to buy the Titan String as she is a bow ranger. I wield Speedy Reply and a heavy crossbow, with heavy crossbow as the currently wielded weapon, though it is sheathed.
But in my main hand, I have a lit torch set up as well. I switch from ranged to melee weapon, up pops the lit torch.
That is the trigger, a lit torch "active", but not even the current weapon. Switched back to melee, torch pops up, un-torch by clicking the little button for weapon proper, and no problem.