Backstab Miss
Well you could try to pre-cast backstab and steal into the target… Otherwise I think this is just something you’ll have to deal with like the rest of us. Could be latency.
with out seeing it cant really tell you what you are doing wrong. But backstab has 180 degree angle of whatever you facing to hit at 130 range. do note though if they move 60 degree outside of the 180 well you hold right click it cause the skill to fail. could be your problem?
such as if they move 120 it will cause self LOS if they move to 240 it auto miss.
it very common way to LOS player in point blank range work on any skill that be channeled.
another possible one it could be is you where immobilize does not allow your char model to turn around could result in same issue of being LOS.
hope it helps if not idk
Let go of wsad before you initiate backstab and your char will turn towards the target on it’s own.