Torquing the string, putting a counterclockwise force on it, will cause left misses. Maybe when you took a deeper hook, you were able to relax your hand more and so stopped torquing the string?
Most left misses are caused by alignment problems: shoulders pointed to left of target, arrow not under eye, drawing forearm pointed to left of target as a result of not coming to full draw, etc. But none of these other than the one I mentioned would be directly affected by taking a deeper hook.