can't insert keyframes before last keyframe

I am not sure if this is a bug or a setting.
If I have a keyframe on frame 1 and another keyframe on frame 100, I cannot insert a keyframe on frame 50.

None of the channels are locked.
Does anyone know if there is a way around this?

I figured it out.
It was a setting.
I opened user preferences, and under the Editing tab,
I un-checked ‘Only Insert Needed’

Now everything works as expected. :slight_smile: