I agree it can sometimes take years for turtles to settle down. You have to realize that when a turtle is out of the water, they feel a bit "vulnerable" because they are outside the water. It's just the way they are.
I would hand feed your turtle as often as possible. One trick that helps is to take their daily food ration & divide it into, say (for example), 5 amounts. Every time you go by the tank put 1 of the amounts into the tank (feed by hand...even go so far as to have the turtle take the food from your hand) so they start to associate you with food. This works wonders, but again it will take time.
After a while, when they see movement, they will associate that "movement" with a person coming to feed them. Plus, it gives you a chance to interact with your turtle often.
