I reproduced your figures, and indeed zooming in the plot, the surface displays discrete patterns These patterns are produced because the values in surfacecolor are discrete (they do not vary continuously) and moreover the colorscale exhibits repeated discrete patterns, that are visible if you are plotting the colorbar.
To understand what’s going on, I have unpacked your code from the function body that creates the surface, and analized the result of each line of code. My first thought was that the full colorscale (of 256 entries) could have blocked the color interpolation, but it’s not the case as you can see in the example given in this jupyter notebook https://chart-studio.plotly.com/~empet/15938/. where you can find more details and arguments that indeed the discrete values and the discrete colorscale caused the patterns observed when zooming in the plot. The notebook can be downloaded to run it again on your system.