Don's recent YouTube fireworks video shows a variety of movement in the convergence in the first 4 minutes. See for example the change in the appearance of the castle from the 1min 36 sec mark (Left and Right images of the castle have nil, or near nil, separation) to the 2min 5 sec mark (Left and Right images of the castle have a large separation). I can't tell whether these changes were somehow associated with panning and zooming in the editing but in that particular time interval there seems to be very little panning or zooming.
Jeff, repeating, I made some corrections to the closer shot clips that fixed the disparity issues after that video was uploaded. Originally, I was not concerned over the original keyframes in that older clip since my test was mainly to check for issues in the dissolves between clips of different frame rates. I took a look at the specific location you mention and the keyframes did need to be adjusted to correct the changing settings.
The one thing I have observed, is if you set an auto correct for a long clip and then slice it up into smaller clips, you really need to go back and do additional auto correct keyframes as the original settings never seem right after slicing the clip up. I don't think this is a bug, but rather just the nature of the beast.
If the cameras and subjects remain static there should be no need to do any more than one auto correct at the beginning of the clip. If you zoom in or out with the cameras, or have subjects change distance along the depth axis, or pan along a perspective depth line axis, then you need to do an auto correct at the beginning of the change, and at the end of the change. This will create a ramp of correction through the image change. If the rate of image change happens then you may need another keyframe set at the point of change. These corrections are needed for twin independent cameras because it is virtually impossible to achieve 100% perfect alignment at the huge distances wide IA cameras are used for. So, we do final keyframe alignment in post.
The horizontal offset keyframe, if incorrect, can generate lots of ghosting. For my completed projects, I set all the horizontal offset keyframes to reduce ghosting. Generally this balances the primary subject in positive, negative, or zero parallax based on the lens focal length, distances and I.A. I used for the shot.