Translated Menu Item Disappears

I have a site - primary language is English and secondary is Spanish. When I translate a menu item string into Spanish, it appears fine when I view the site in Spanish. However, the instant I "translate" a node and set it to English and it's translation to Spanish, the Spanish menu item disappears. The only way I can get the Spanish menu item to appear is to change i18n's "content selection mode" to "All content. No language conditions apply." For the Spanish translated node, I don't set the Menu settings since they are set in the English version - the only thing I change is to add the URL - es/node1 so that when I click on the menu item, it goes to the correct translation.

This was working at one point but now it seems to be having issues - can you point me in the right direction to at least start effectively investigating this?

Thanks!