This bug is very difficult to reproduce and I haven’t yet found a consistent way to trigger it, but sometimes after using shift my next attack (Flurry, on Q) is completely disabled until I wait for some amount of time or use another skill first.
I think it has something to do with holding click-to-move at a destination past the distance of shift and releasing the click during the shift while also attempting to use a skill.
approximate character sheet can be found here Marksman, Level 82 (LE Beta 0.8.1b) - Last Epoch Build Planner
disregard acid flask as I specced out of it and im still getting the bug.