Before anyone else comes up with more conspiracy theories...
This is almost the same problem as
this one. Copying is your friend, and enemy.
What a peculiar requirement.
The only requirement is that you understand what is happening in your own code and how that affects your SFML objects. Anybody proficient in C++ (and STL) and who understands that sf::Text keeps a
reference to sf::Font can add the picture up for themselves and see what is wrong. Although you didn't show us how you populate your
board.GetTexts() container, based on your code returning a
copy of
text, I can tell that you probably made the same mistake there.
Don't pass copies around as much as you are doing now. SFML classes, even when built in C++11, are not enabled to be moved yet. Your code, if it runs without crashing, probably runs horribly slow because of all the excessive copying that is happening.
If you want to fix this crash you were having before you resorted to
shotgun debugging, you should read up on what the container does when you add new elements to it.