Note the pronounced angle in the following photograph of the spinner posts on the original first-season robot:
Now, compare this with the spinner post from this third-season publicity shot:
Also, compare the first-season spinner post with this screen grab from the third-season episode "The Anti-Matter Man" (episode 74, original air date: 27 December 1967):
This is quite a contrast from the first-season robot's spinner posts seen in this screen grab from the first-season episode "Island in the Sky" (episode 3, original air date: 29 September 1965):