[transitions] stop 0 frame being the end frame

As far I can see all my transitions starts at 0:01, the frame 0:00 copying the end frame. I would like this to not be the case in my project :

My Object : A crane

Animations/state (Animations are not looped) :

1. the hook goes down and up / grab
2. the crane rotate left / rotate_left
   
3. the crane rotate right / rotate_right

Transitions 1 to 2 and 1 to 3 are bugged. Let's look at the crane rotation. It should be :

1. 0°
2. grab -> rotation stay the same : 0°
3. First rotation key : 0°
   
4. rotation -> +/- 45°

But instead, as the first frame copy the keys from the last frame, it is :

1. +/- 45°
2. grab -> rotation stay the same : +/-45°
3. First rotation key : 0° : GLITCH
   
4. rotation -> +/- 45°

Thanks for any advice.

Edit : animations loop state