Blender only Renders 50% of an Animation?

Okay so i have a problem
I am doing an Animation right now and when i press Animation it only Renders 50%(the animation has 1200 frames but it only renders 600 frames).
also it doubles the start frames. So if i would start at frame 5 it would be frame 10(5*2), if its 0 its still starts at 0.
Also it closes on its self (while Rendering the animation)

Why are you not showing us your render settings ?? Why do we have to use guesswork ??
Have you set the frame range from 1 to 1200
Have you set the frame step to something other than the default of 1
Have you changed the Time Remapping values in the render settings
Have to enabled the ‘Fields’ option in the render / post processing settings