Q or Select Previous Target

[Blue Jay]

Every time I set my Q key to what I want it, and it has nothing else bound to it, which is "select previous enemy" in case I pass it with TAB, I come back after taking the night off or whatever, and it's unbound. Every time. It was reverting me to its default, but it stuck when I unbound it to that. Still, it will not remain bound to what I wish. Can you help me?