Memory pairs game - multiple answers possible?


I'm trying to create a pairs game where there are multiple options for a correct pair e.g. in a game about the categorisation of different food textures (it's a speech therapy thing!), thin custard could be matched with both pureed fruit and tomato soup, and rice pudding could be matched with both thick custard and chocolate mousse. I've made the card pairs as, say, rice pudding + thick custard, rice pudding + chocolate mousse and and have uploaded the identical rice pudding picture each time but when I come to play the game, these are not recognised as being the same. I've attached 2 screenshots to show how rice pud + thick custard is recognised as a correct answer on one occasion and not on another. It's as if there is a separate 'version' of the rice pudding pic for the custard and the mousse, even though what is being uploaded is identical. 

Any idea how to get round this?? Thanks!