Why bother with the carbon freezing at all?
It would be the most effective way of bringing him to the Emperor without incident.
Instead of something believable we got some elaborate plan where Vader meets Luke alone and tries to get him in a carbon freezing chamber which fails and then they duel with lightsabers. How contrived.
Actually Luke and Vader started dueling and early into the duel Luke falls into the Carbonite chamber. The duel was a distraction to get him into the chamber. When that failed he continued the duel to test Luke’s abilities until he stopped playing around…