Changing State of Next Button

If there's a trigger that is set to change the state of the next button to hidden when the slide starts, then when you revisit the slide, the next button will be hidden when the slide starts. You need to add a condition, for example change it to hidden when slide starts on the condition that variable = False.

I'd create a T/F variable (SlideVisited) and set it to False. Then add a trigger to adjust the variable when the state of ABC are visited. 

Then modifiy the trigger to change the state of the next button to hidden when slide starts on the condition that SlideVisited = False. The first time, it's hidden. Once they've completed the slide and revisit the variable should be True.