I'm not good enough to tell you exactly whats going on, but the problem is in your "second pull" or when the bar goes from mid-thigh to around your navel. Your hips are too high, so when they drive through they push the bar out and away from you, instead of getting underneath and elevating the bar.
The full snatch with a squat catch is a long, long range of motion. Sometimes you get so good at jerking the bar off the floor and squatting underneath it that you can kinda "cruise" through the second pull, and rely on the first pull(off the floor) and the deep catch position while neglecting the middle of your snatch.
You just need to work on the timing of your second pull. In my opinion the best way to do this is to break the move down into more manageable portions. Try something like...
Deficit Snatch Grip Partial Deadlift 4 sets of 5
-Stand on a plate, with a snatch grip pull the bar to just below your kneecaps. Pause for a brief 1 count, then return to the floor. This will teach you to get over the bar, keep it close, and really control the first pull.
Clean Grip High Pull 6 sets of 3
-Kinda like a deadlift with a shrugg at the top. Except if you push your hips through too early you'll guillotine your nuts on the shrugg. This will teach you scrape the bar up your thighs keeping it close, the correct timing for the second pull.
1 Arm Power Snatch with Dumbbell 6 sets of 3.
-Let the dumbbell hang in front, kinda between your legs. Brace your off hand on you knee so you don't twist as you snatch it up. With the dumbbell in the "middle" you're in a tremendous position to really explode and really rip the weight straight up.
Power Snatch from the Hang 8 sets of 3
-Bar in hang position, not on the floor. No squat to catch, just drop the hips a little. You can't rely on the jerk off the floor, or the squat catch, it's all second pull. You'll have to figure out the timing, or the bar won't get high enough. This will really teach you to pull straigh up and keep the bar close to your chest.
Do this until your power snatch exceeds your current full squat snatch.