Yes, the FF rendering problem goes away with that change (at least on the Mac). Thank you!
However, this was actually a looping animation and adding this immediateRender parameter has stopped the resetting (i.e. canvas clearing) with each new loop.
Nothing I seem to change in this code (i.e. adding .remove() etc. ) seems to reset the canvas after each loop is finished. Is there some magic method or syntax that can achieve this?