Unexpected movement between keyframes.

I’m starting to notice a rather strange problem that if I have an object or set of objects that do not move between two keyframes Synfig occasionally inserts unexpected movements; such as having having said objects move off to the side and then back to the original position in time for the next keyframe, instead of just standing still. Though comparatively rare, sometimes keyframes are altered to match the unwanted movement. What makes it really odd is how synchronized this is. I’m mostly working on animating a character at the moment that is composed of multiple parts in a pseudo paper cutout style. Some examples of strange behavior include:
One entire arm (three objects) shifting up and the other arm shifting down.
A shoe and pant leg shifting down between keyframes as if the character suddenly developed a very long shin.
The character’s knee (simply where two objects meet) suddenly pulling to the side.
The character’s entire upper torso shifting up while the bottom of the torso remained in place. Even stranger, the arms were hanging at the time and were un-stretched, unlike the torso.
A single duck radically changing position for no apparent reason.
The character’s knees move closer together, while the rest of the character’s body moved up in sync.
Something with a rotate layer rotated to the left and back between keyframes.

I had previously thought this had something to do with rotate layers and resizing objects between keyframes as these objects seemed the most likely to cause problems, but now it seems to happen randomly to any objects that move. At the moment I’m fixing things one frame at a time or simply duplicating the keyframes on every inbetween frame as a work around. Something else odd that happened while trying this was that I when I duplicated the first keyframe onto the frame right between the first and final keyframes, the unexpected movement would then occur between the new keyframe and the final keyframe.

Does anyone else have this problem? Is this a bug or is it some random thing I’m doing wrong without knowing it?

I’m running Synfig on Windows 7. If there’s any other relevant system information that’s needed just let me know. Also, I don’t have an example file with the problem, but I can set one aside if needed. It happens often enough that it wouldn’t take long before it happens again.

Thanks for any help.

I is not a bug but a common unwanted behaviour. See this thread:
Solution: Between two steady keyframes use linear interpolation.

That was it! Thanks so much for the help. Somehow I had managed to completely overlook interpolation while learning about Synfig. I guess that’s the catch with powerful software, it can do a lot but it requires knowing a lot about it.

Thanks again for the help.

Also, is there a way to set a default interpolation method? I’m having trouble finding anything about that on the wiki.

Yes, it is a bit hidden.
Modify the drop down menu that is at the bottom of the toolbox. It is set to TCB by default but you can change it.
synfig.org/wiki/New_Layer_Defaul … erpolation