If the last step of the workout is set to "Lap button press", pressing the lap button at the end of the workout will create a new lap, but the workout will not end. In the other steps of workout except the last one the lap button work correctly and goes to next step. When the last step of the workout is set to a time or distance, the workout ends correctly.
Did you ever find a solution? I just moved from the FR220 to the 255 and this has been an issue with all my programmed workouts so far on the new watch. I had no issues with the decade old watch.