remember the translation issue
this is a part of the plugin docs, that i think it could help
https://qtranslatexteam.wordpress.com/faq/#CustomFields
please take a look, and see if the parts in the theme that have the problem need any fix

the places that have the problem
the cart: enter this link and add the item to the cart
then open the cart, you will see the title in a this format
[:en]English Text[:][:xx]Other language Text[:]

this exist also in the previous and next buttons pop ups (if the product shown is multilingual)

and in checkout page