When trimming a clip which contains a LinearTimewarp effect via flatten_stack or the underlying track_trimmed_to_range the resulting source_range on the trimmed clip is often incorrect.

To illustrate the problem see the screenshot below. When the tracks "Overlay B" and "Main B" are flattened to produce "Flattened B" the 2nd clip in the output (here named "Wrong Start") has the wrong start time. It should be "01:00:07:09" but instead it is "01:00:09:12".

For comparison, when I slice the timewarped clip in Avid Media Composer, I get the correct result in this screenshot. Here we see that the clip "Sliced in Avid" has the correct start time "01:00:07:09", and so does the resulting "Correct Start" clip after flattening.

This bug is due to the fact that track_trimmed_to_range makes no attempt to honor the timewarp effect on the clip.