Thanks for the suggestions. I increased buffering to 10s and still get some momentary audio freeze. I also tried, in addition, the change to config.txt. After rebooting my rpi I noticed I still have some random momentary audio freezes.
I reverted back to original configuration.
I thought I would play around with some other parameters. In Player/Options/Advanced I unchecked Play as HDCD, and also in Player/DSPStudio I unchecked Volume Levelling. I have not noticed any audio freezes with these changes. Coincidence or not. I might fiddle more to see if turning them back on individually makes a difference, but that is for another time.
As an aside I checked my stretch rpi to see whether these settings were checked or unchecked. They are checked. The only other difference between the two from what I can see is that the stretch rpi is connected to a better DAC so no conversions are necessary for music above 96khz. I can't recall at the moment whether the freezes were only for music at 192khz being converted to 96khz. Again something to check for another day. Still I do know that prior to switching to buster that this music did not freeze.
So for now I am satisfied with the set up.
I may swap out my SD card to see if the buster version works smoothly with my better DAC system, but for now I will leave that one running from stretch.