Mine has a similar issue. I have it set to where I can get pretty close groupings where I'm aiming, but only because I know to aim slightly low. I suspect the recoil it has may slightly impact it, but it's probably just because my scope is the cheap one that came with mine. If your using the stock scope, that may be your answer.
You could run a ballistic calculator to see the trajectory at given ranges.You could adjust your scope to lower your impact at 20 yards by about an inch or so also.Personally I don't take 40 yard shots at animals.Hawke optics used to have a free calculator.
The arrow is not rising from 30-40, it is just not dropping as much as you are holding over for. The hash marks in the scope are not calibrated correctly to the speed of your setup. Yours may end up 20,29,36,43 or something like that.
If you like your current bow and arrow package you have several options. See where it shoots with your current setup and tape a yardage chart to your stock for reference. Go to a slightly heavier or longer arrow and/or broadhead to see if this brings the trajectory closer to the 20,30,40,50 you desire. Upgrade to a new scope with a speed dial that allows you to tune the scope to the speed of your bow. Sight in at 15 yards or 25 yards and see where the others fall.
What DPMS said about adding weight to the projectile worked perfectly for me back when I was figuring out my crossbow. With a 100 gr. broadhead, it was 20 fps too fast360 fps), and the stadia lines in the scope were off accordingly.
I bumped it up to a 125 gr. broadhead and chronographed it again: the velocity was then spot on to the factory advertised speed (340 fps) and the stadia lines were dead on out to 60 yards.