During Tinman's song, Toto was on the left side of the screen, then when they cut to the view of Dorothy and Scarecrow, Toto is miraculously changed sides in that split second. Watch carefully as it happens only once
This is true... it shows Toto on the left of the Tinman after Dorothy and the Scarecrow are whispering to each other, and then IMMEDIATELY to the right of the tin man as he starts to sway back and forth.