I did another render in the same scene that was not so near the origin and it doesn't have the seam. Actually, the two were rendered using two different systems and I think that I haven't yet upgraded them all to the same level so I am now thinking that the problem may be due to an old version.
[LATER]
I have checked all versions and all systems are updated to the same version so the seam must be there because the camera is close to the origin.
Here is position information for the camera that had a visible seam:
Position: xyz: -1.6489, 500, 84.1943
Rotation: xyz: -15, 0, 0
Render Resolution: width=8192,height=4096