Triggers not working as expected

Hi, my triggers aren't working as I would have expected, and I can't for the life of me work out why!  The scenario is:

I have a slide with multiple layers.  When boxes are clicked on the base layer, the learner is taken to another layer.  Once the layer has been reviewed, they click the "Back" button.

What I would like to happen is: if they have clicked each of the boxes on the base layer (and seen each of the layers), the "Back" button on the final layer they see takes them to the "End" layer.  If they haven't clicked all of the boxes yet, the "Back" button should take them to the base layer.

I have set up variables for each of the boxes, so that the variable changes from False to True once they have clicked it.  Then, with the "Back" buttons I have put in the following Triggers:

1. Show layer End when the user clicks Back if X variable = True AND Y variable = True (AND all other variables = True)

2. Hide layer This Layer when the user clicks Back if X variable = False OR Y variable = False (OR any other variables = false)

I have checked that all the variables are changing to True, but when I preview the course I never get to the End slide!  Even though all variables are set to True, the final time I hit Back, it stills goes to the base layer.

What have I done wrong?!

Thank you