Wanted to check if I have interpreted this correctly.
A unit with an independent character attached is in difficult terrain. Assume the character is somewhere in the middle of the other models. The player wants to separate the character from the unit in his movement phase (so they can attack separate targets). He rolls a double 1 for their terrain test.
Now the character cannot leave the unit because it is impossible to move them so that they are more than 2" apart. Therefore they have to continue to shoot and assault as a single unit until the player's next turn.
Does that sound right?