thank you for reaching out to us. Your video is fine, one has only to increase the resolution since Google Drive always starts streaming with a low resolution. The behavior shown in your video is indeed odd, but the problem with the video is that you never show the attribute manager for target expression tag which sits on the camera
Script_Target_Tag. And therefore also not if that expression has something linked in its target parameter. Given your results, I would assume that this is not the case.
I just tried it in R21, and a programmatically created target expression works fine for me. For details, please see the screencast and script at the end. If the problem persists, I will have to ask you to share code and scene files. So that we can understand better what you are doing.
My results (click the image to enlarge it):
Very simple script to create a targeted camera for the selected object:
"""Creates a camera with a target expression linking the currently selected object.
if not isinstance(op, c4d.BaseObject):
raise ArgumentError("Please select an object.")
# Create a camera object and insert it into the document.
camera = c4d.BaseList2D(c4d.Ocamera)
camera.SetMg(c4d.Matrix(off=c4d.Vector(300, 0, 0)))
# Add the target tag to the camera and link the object.
tag = camera.MakeTag(c4d.Ttargetexpression)
tag[c4d.TARGETEXPRESSIONTAG_LINK] = op
# Execute main()