Welcome to the forums, @Cleo
It's kinda tough to troubleshoot blind (a codepen would be super helpful) but it looks like your "items" only consists of one element with the ID of dd-heading. So perhaps your selector is wrong? Again, I don't know how you set up your HTML, so it's difficult to diagnose. Remember, though, you're not supposed to use the same ID for multiple elements (they must be unique). Did you mean to use a class instead maybe?
Also, in your out(), you're simply playing the timeline which probably isn't the best idea because what happens if someone rolls their mouse over...and then very quickly rolls out (before 1.5 seconds has elapsed to reach the pause)? Nothing would happen. The animation would just keep playing. In order to get that out() animation to play, they'd be forced to wait the full 1.5 seconds before rolling out. That's just a logic issue with your code, not a GSAP thing.
Maybe it'd be simpler to just build an animation in the over() and a different one in the out() so that they can dynamically determine their starting values based on whatever the properties are at that moment (even if a previous animation is part-way finished).
If you still need some help, it'd be awesome if you could provide just the simplest codepen that demonstrates what you're attempting.
Happy tweening!