I think you've identified one important cause of hitting left, but don't be surprised if you start hitting left again sometimes, as this has a number of different causes.
I find that the first few shots I shoot in the morning typically hit left, and again after I get tired. I think the cause is not coming to full draw. With my string forearm at an angle to the arrow (viewed from above), it is easy to pull the arrow a little to the left on release, since my forearm is not pulling straight back in line with the arrow. It is easy to see this, as I can see the arrow in my peripheral vision pointing toward the target, but then it veers off to the left when I shoot it. It causes me to have 4-6" misses to the left until I correct the problem. This is exaggerated if I have any tightness in my string arm muscles or hand; in fact, I can get away with not coming to full draw if my string arm and hand is completely relaxed, but the slightest tension in my string arm combined with not coming to full draw guarantees a left hit.