I am using the rotoscoping effect on a clip, with a larger number of keyframes.
Then I save the effect and apply the saved effect to another clip.
On the new clip, however, I find that all keyframes have shifted by 30 frames to the right (and the keyframes within the last 30 frames are lost).
Exactly the same happens when I copy the effect to the other clip (instead of using the sacved effect).

Does anybody have some advice what I might have done wrong?
Or is this a known problem?

If I get this to work, then I may have a nice way of making lightsaber effects in kdenlive.

--- Edit:
I have now found the reason:
In the timeline, the first clip (for which I had defined the keyframes) did not start with the first frame, but with frame #31.
It seems that the keyframe numbers in the effect are not referring to the frames in the timeline, but to the actual frames of the clip.
This explains the observed shift.
Since my 2nd clip (the one to which the effect was copied) is simply a "color clip", I could easily enlarge it by 30 frames to the left.
Now the keyframes are aligned between the original effect and its copy.