GUI Axes Shifting Slightly Between Plots

[JP]

I have a routine called "PlotScene" that I used to use with simple
figures and I call it each time through the main loop (so the routine
updates the current plot and you see an animation).

I am trying to use this routine with a GUI axes now, and while it
seems to work, every now and then the GUI axes, along with the
colorbar and legend "jitter" a little bit and appear to jump ever so
slightly to the left or right.

Any ideas what the problem might be and/or how to fix it?