Unexpected file playback freeze and plot corruption

[mjbb2]

I'm using a data file I previously recorded. Playback at 115200 works fine. Doubling the baud rate to 23400 causes the plot to display nonsense and freeze.
See attached picture. At 27:23 I increased the baud rate. No error messages are displayed. After disconnecting the source the plot displays more nonsense for several seconds then recovers and scrolls the bad plot off to the left. With no active connections and nothing being plotted, the MegunoLink CPU usage now varies between 27 and 29%.

[mjbb2]

More information:
At 230400 the progress slider does not move at double the speed of 115200.
Instead it jumps around wildly. It looks like the baud rate is not being limited at all.