The time update is optimized to schedule the update as little as possible - instead of scheduling it every second, instead it sees that the line and label would only move in 5 minutes and schedules the update for half of that - 2.5 minutes.
I did find one issue in there where if the unit was changed to a large one (like month) using the toolbar and then swiped back into seconds the time line would freeze for a couple of seconds - I hope that this was also the cause for the freezes you noticed. It will be included in the nightly build released later today.