im getting those since i started making animations, here are two examples of what i mean:

example one:
i have an animated door with 4 parts/bones. bone_l ;bone_r and bone_l_2 and bone_r_2
bone_x_2 are childs of the approprieated bones. on the first 20 keyframes only the childbones move
on the next the parentbones move and the childbones with them. but in the first frames bone_l moves randomly forward and backward to be on frame 20 in its original position, that doesnt make sense?!

example two:
an unitanim has keys on frames 1, 30 and 60 the left calf bone rotates a bit on the x-axis until frame 30 and then moves back to its original postition until frame 60. but between frame 1 and 30 it randomly rotates on the z-axis!

is this a bug or a logical result of wrong bonerotation/translation?

You may have to go into the animation editor and set all animations to linear.
Open the editor select a bone find the ^ looking symbol and press it.

thanks for your help
the trick worked on the door but not on the unit, here is a small screen of the movement (the calfbone should be rotated in such a way that the foot touches the ground correctly)

you did do the linear thing for all the bones you have moved right?
Remember the song. The toe bone is connected to the foot bone the foot bone is connected to the calf bone the calf bone is connected to the.... okay I'll stop now.

But one of the other bones could actually create the result you are seeing.

i allready checked that, even if i remove the keyframes on frame 30 for the thigh and calf, it still rotates >.<

and i dont remember nor know the song...