Beats me, but I've seen problems like this before. On the MeTV 'oldies' channel, episodes of The Dick Van Dyke Show and Buck Rogers in the 25th Century often (to my eye) have the "shot on tape" look to them, but I know for a fact that both show were shot (and edited) on film. Also, on the...
Shot on tape? Nope, no way, not an American drama on a major network. Now, post-produced (edited/assembled) on tape? Most likely, as that's how many US shows were being done by the late '80s.
Perhaps that last reunion film was edited on 35mm (rather than tape), or prints were struck so it...