You can lose paths due to low affection points; you might have lost Judie's path long before the game actually acknowledges her path as lost. gudrald is partially correct, you need 6 affection points to avoid losing Judie's path at that point. Seeing the bathroom lewd scene helps but is not required.
I struggled with this too, so I made a mod that can predict path loss early and save you from having to reload a save you made hours ago.