Have Millwall 15/2 to win the play-offs and 8/1 to win promotion. They have Preston 50/1 and 66/1 respectively.
In League One Derby are 11/2 and 6/1.
So these aren’t mistakes.
I bet fairly regularly but haven’t noticed this before. So you have to ‘shop around’ so to speak even on the same site to find the best odds.