Copyright? Permissions? Who knows? I don't think it would have been a good idea to have had him come back a third time to play a so similar character again and confuse the audience who remember him from the previous show! I mean Mark Lenard did two shows in the first and second seasons like Woodward, apart from Diana Muldaur who appeared as two different characters in seasons two and three I don't think there was a guest star on the show who did three main appearances was there? And I'm not counting people like Paul Baxley or the third extra from the left in this or that show...
JB
JB