Revealing mistake: When Diana is supposed to cut the power cables to stop the timer, just before she cuts the cable, you can see that all the cables are already cut and have a large, obvious seam in each of them. Then, when her hand goes through them, they all cut right at the seams.
Deliberate mistake: When Wonder Woman is bouncing around in the padded room, there's one part where you can tell the stunt double is not Wonder Woman.
Continuity mistake: When Wonder Woman tries to escape from the building, she's in the room with the padded floor and walls. Her heels are missing from her Wonder Woman boots, but they were on when she was in the hallway.
Answer: The transformation twirling was invented for the 1970s TV series only, to explain her quick change from Diana Prince to Wonder Woman. However, it would have been nice to do a little spin homage in the movie.