The 2 engine, manually flown missed approach is one of the most mis-flown procedures. How often do you practise one?
And this true comment invites the question of what the heck are we doing with one of the best training devises (sim) if there is a known problem and it's not being practiced?
Further, why is it messed up? On B737 the normal 2 engine G/A is flown as F15. If this is a manual manoeuvre it is like a F15 takeoff; the main difference is PM has to select the flaps. Other than that just press TOGA, select F15 and follow the FD. What contributes to causing a mess up is that some company's SOP's fly a G/A different from a normal takeoff. They rush to retract flaps at 400'; why? they fly it manually all the way to flaps up; why? A G/A is not a rushed affair, or should not be. It can be as relaxed as a takeoff and then it is conducted and executed correctly. If you listen to the 'mouth music' and calls of some G/A SOP's and then compare to a normal takeoff it sounds panicky, so guess what happens.
Keep it calm & simple for best results.