Luke wrote, that Judas Iskariot left AFTER the meal (Luke 22:19-21) . For JW-thinking this could not be. So Luke must be wrong.
Look at insight-book "Judas":
"Immediately Judas left the group. A comparison of Matthew 26:20-29 with John 13:21-30 indicates that he departed before Jesus instituted the celebration of the Lord’s Evening Meal. Luke’s presentation of this incident evidently is not in strict chronological order, for Judas had definitely left by the time Christ commended the group for having stuck with him; that would not fit Judas, nor would he have been taken into the “covenant . . . for a kingdom.”—Lu 22:19-30."
This was some month ago an eye opener for me. GB tells us, Luke is not in strict chronological order.
Luke 1:3:
" I resolved also, because I have traced all things from the start with accuracy, to write them to you in logical order, most excellent The·oph′i·lus..."
(there is a nice thread here on jw-net about this point - I just can not find. )