Different behaviour when loading a scene for the second time

I'm having a terrible time with a Unity application I'm making.

The structure is that I have 3 scenes: a "Title" scene, a "Menu" scene, and a "Game" scene. The users start at the Title scene on load, and advance on a button press to the Menu scene. From here they select a puzzle to play. Then we advance to the Game scene, which is populated using data from the selected puzzle.

The problem: when I return to the Menu scene from the Game scene (via a button), and then attempt to load another puzzle, when I return to the Game scene, nothing gets populated. Something is breaking, I assume due to something having changed in some way.

Avenues I've explored:

-Static variables. I had some, but I've since removed them all.

-DontDestroyOnLoad objects. I still have 4 objects with this behaviour. However, they are all created on the Title scene, which is never returned to, and so I'm fairly sure they aren't being duplicated or anything like that.

I desperately need suggestions for something to explore. I'm rapidly running out of ideas.