Sounds like your setup is causing the problems, or at least someone with your setup would tend to be weak at the top.
People who use a closer grip and less arch tend to be strong at the bottom because there is more stretch in the chest at the bottom, and a more stretched muscle can often produce more explosive force. But having less arch and a mid grip is going to create a very long stroke. By the time your halfway through your bench stroke I'd be locked out since my bench stroke is essentially only a few inches long.
I'm a big fan of using your setup to get as close as possible to the results you want before you actually start to mess with how you perform the lift. It's easier to change what you do before you start the lift than what you do when the weight is in your hands. I think you should experiment some. Try arching more. What will probably feel like an extreme arch to you is nothing compared to some benchers. Focus on all the standard keys;
1. Shoulder blades tucked back like your trying to squeeze someone's finger touching the middle of your back.
2. Make it so the only parts of your body that touch the bench are your traps and your lower glutes.
3. As you lower the bar, try to shove your heals into the ground hard. Feel like your moving your body TOWARDS the bar instead of allowing the bar to move towards your body. Pushing specifically through your heals tends to keep you from lifting off the bench like most people do when they try to get a lower body push. It also squeezes the glutes which pushes your body up.
4. Keep your armpits tight. I like to think about how it would feel to try to hold a paint can under my arm just by squeezing it between my arm and my side.
I'm a big believer that your bench press setup should be extremely uncomfortable. I get terrible cramps if I don't thoroughly stretch my lower body before doing bench, far more than I do before squatting. I'm so uncomfortable in my bench setup that I can't do more than 3 reps of any weight, but it works extremely well for me. I added 40lb to my paused bench in 1 week by focussing on form alone.
Current PRs at 242, raw w/ wraps- 525, 355, 605, 1485
Roboro tui, perimo vester adversarius
(Build yourself, destroy your enemy)