Can't change parts

I'm not sure if I pressed something for this to start but I was messing around in the parts menu, and whenever I'd try and change parts the selector would turn orange and not change anything
if anyone could help fix this that'd be grand

 

At the bottom there should be a little checkmark called apply changes automatically, uncheck that, or hit apply, it turns orange letting you know which part you selected, because you can pick multiple.

 

ohhhh interesting. Makes sense, thanks boss

 

Thank you so much i thought my game was broken.