take a look at this
http://cgterminal.com/2011/05/29/keyframes-and-f-curves-in-cinema-4d-tutori... and if you're in 13 check the Help/Tutorials/Animating With Cinema 4D - The Basics/Animation Methods.
You have to know what F-Curves are, where to find them (Timeline) - your problem is simple your f-curve for the faceplate motion (whatever parameter(s) you animated to get the motion) is being interpolated smoothly at the second keyframe and is shooting past the target value you wanted. To stop it you just have to clamp the value of the second keyframe or set the second keyframe to linear so it goes straight to the third keyframe without 'overshooting' the value you want it to hold.
It probably won't make sense until until you find out more about f-curves but it really is simple
