It's probably due to your CPU settling down.
I know on my end, even though the screen loads and I can swing, the game still isn't fully loaded (which is seen by the high cpu utilization that drops down after a few seconds).
If I swing with high CPU utilization, the swing meter can be very erratic. If I wait for it to settle down, the meter is usually consistent. Though there are times when CPU util will drop, but then spike back up unexpectedly. ALL the CPU util are being used by the browser running the game from my observations.