The ROTJ line I never understood was Vader saying ‘leave them to me, I will deal with them myself.’ Then several seconds go by… then the Falcon gets clearance.
What was Vader doing in those few seconds? Standing there and just thinking about it?
Yes, he was deciding what he was going to do. He knew Luke was on the shuttle. I think there was genuine indecision on Vader’s part about how he should proceed.
Remember, enough time had passed since the end of Empire, and Luke refusing him and getting away would have taken an emotional toll. Vader is kind of a broken man in the last film, a shell of his former self. His plan to turn Luke and overthrow the Emperor is hopeless. Palpatine knows he’s a traitor and keeps him on a short leash. I doubt Vader really even sees a way forward, and that’s why he comes off as resigned and conflicted.