This has happened twice now, not sure what causes it. This is on a melee flurry blade dancer.
The first time it happened, every few flurries the hits would register, but for some of the flurries none of the 3 hits would register.
The second time it happened, only one of the hits from every flurry would register.
Obviously this decreases DPS by a lot. Both times logging out and logging back in fixed the problem. This only happened after a long gaming session, after a couple hours or so. Next time it happens I’ll record a video.