Flashcard text fading but just on some cards

Kia ora koutou (greetings everyone)

I've got a flashcard set with a centred image on the front, and about the same amount of text on the back. 

On two of the six flashcards the text fades towards the bottom. I'd rather it didn't! 

I've tried clearing the formatting and even deleting and redoing. 

What am I missing?? 

Nga mihi nui (huge thanks)

Ann