Buttons Trigger Changes Not Saving

I have three buttons on a slide. Each button has a different name. For some reason, when I click on a button to change the trigger, Storyline won't allow me to change the "Jump to Slide XX" to another slide. 

All three buttons have the same trigger, and I can't change them. I have tried deleting the button and recreating it, and that hasn't worked. 

The highlighted Deliver Training button in the screen show trigger is set to the Adult Learning slide, and so do the other buttons. When I click on a different slide and try to change the trigger, Storyline changes the highlighted button to Deliver Training button. 

What am I doing wrong?

Thanks in advance for your help.

Richard