May I offer that "jumping the string" is sort of a mis-speak to me. The deer are not "jumping", but rather squatting to load their legs muscles for flight. You can demonstrate this yourself. Stand straight and tall, with legs absolutely straight. Try to jump say 6" up? Cannot do it without what? First bending your knees to load your legs.
In my now going on 50+ years of archery hunting deer, I can count on one hand the number that I could possibly say did not flinch, drop, twirl, etc. before the arrow hit home. And I have had about an equal number missed that got out of the way before the arrow could strike .... including a 27 yard broad side shot at so called "relaxed" deer when I was using a bow that supposedly IMO'd at 300+ fps. She had time to completely wheel 90 deg. and haul tail. She had her head down and was munching on clover when I released! Go figure.
What I think you may be dealing with are: (1) A noisy bow. Have someone stand 30 yards or so off to the side and listen for any unusual rattles, metallic sounds or loud slaps when you fire. If that is the case, try to mitigate by making sure everything is where it should be and is tight. If you are not using vibration suppression stuff, try that. (2) You are simply aiming too low. While I will never take the aim point out of the killing zone, i do aim low ... especially on broadside shots. I put the pin abut 1/3 up from the bottom ... no higher.
As far as speed? I have killed hump-teen deer with my original 1962 vintage recurve. It was a 45# pull, 60" laminated limb bow ... cedar arrows, 6" helical feathers, and 150 gr. broad heads. What would it do fps-wise? I have no clue. Maybe 150 ?? I killed deer and feral hogs cleanly out to 40-45 yards. No more :jumping the string" issues than with my SQ2. Sure, velocity = less arrow drop/linear foot of flight traveled. But I don't think that is the issue here.
Now form may be? You may be pulling off the target, anxious to see if and where you hit. Easy trap in which to fall. Try this if you don't already do it. As you release, keep your self very quiet, and head still, loose grip ... eyes watching the arrow's flight all the way to the target. Then think about watching where the deer ran off to. I find that this helps me "follow" the arrow.
Good luck. And show us the pics.