One of the reasons why I wanted you to try my demo site is because it’s version 1.7.7 and to see if it worked for you. So it sounds like it’s something related to changes you might have done with the menu CSS in your child theme. I’m not sure off hand what I changed in the new version with the menu css, but that could be it in conjunction with whatever it was you changed. Your conditional statement should not be affecting it from what I can see.
As you mentioned, caching could be the problem too….might want to check on that in all areas caching is done.