Short description of error
This is a re-do of another other bug report I filed earlier this month (T63304), now that I understand it a lot better I'm filing it again with a more accurate description and demo file.
In the video editor, if you one or many scene strips, on updating the frame the camera bind that the playhead falls under will most likely not be applied until the following frame.
So, when you place the playhead in a region that uses a different camera bind, it usually does not update unless you update once more in that same region.
This is also the case in rendering animations using the video editor.
I've created a demo file that perfectly illustrates this problem below.
This bug urgently needs fixing.
Exact steps for others to reproduce the error
Instructions for demo:
If the playhead is in the BOX region, it should show a box, if it is in the SPHERE region, it should show a sphere. I estimate about 80-90% of the time it doesn't update correctly. Why there is an element of chance I cannot work out.
Try moving the playhead around between markers (which indicate a camera bind in the strip's scene) and notice how the bind almost always fails to apply.
Now try jumping from region to region and notice how the camera bind is almost always 1 step behind, so it is never applied, place the playhead within the current region and it updates without fail.