Old post, irrelevant information by me was provided and a new updated post has been posted.
I’m not sure if it’s the best solution but perhaps easier to read.
I’d have two tweens made, one for clockwise and anticlockwise respective the the panels rotation. It seems like you’ve already got that down in the example you showed. Then each time it flips, change a bool value either within the script or as a value in the model for Reverse.
Once it comes to playing the tween for each panel have an if statement for if reversed == true then… Play the different tween.
That’s how I’d do it personally, I can imagine there is a simpler and easier to read solution but 
So, the issue isn’t that I can’t get it to flip back, that’s actually fine and I did exactly what you described above, the issue is that when the entire model is rotated (panel and the accompanying parts like the hinge and border), the rotation by 180 degrees doesn’t correctly rotate along the axis of the hinge like in the video above, rather it spins in a circle or in some other weird direction, that’s what I am having a hard time reconciling.