You are correct, I just find out that paused tween will only resume to play once. While selecting flip flop again will reset the tween progress to 0, which caused the problem with the boundary.
I fixed the resume/pause state to correctly return to its former state, if it was a flip flop that is paused, it will resume to flip flop. If it was a loop that is paused it will resume to a loop.
Please try the fixed litetween below, I hope this one will fix if for you. I also updated the thread with this fix.
LiteTween FIX PAUSED