What you should do is basically do lots of air turns.
With the Super Katana you need to be a bit careful not trying to touch too often, that will stress the shoulders too much.
Also, just like you describe, when you're bringing it down ATM you're not strong enough to bring it down in the correct path.
So what you need to do is to avoid full lifts for now.
Shift between air turns and Board presses.
Air turns are the way to go for a proper path.
While (high) boards will help you get that lockout power.
Try doing close grip benchpresses on your second benchpress day. Perhaps work your way up to 6 sets of 3 reps for around 70-80% of your 1RM.
You really need to get strong in the delts so you're able to hold the shoulders locked into the bench.
Ok this is the most helpful advice I have received so far. Most of the rest of the advice I got kind of ignored the problem I'm actually describing - a lack of strength to take the bar down in the right path.
What exactly are air turns? Just partial presses? Thanks for this