D3 JS Exported Maps Image Quality Issue

Question

We are using d3.js to create the maps in our application via reading .csv file that has latitude and longitude to plot the location but sue to huge data (~200k latitudes and longitudes in the .csv file) the maps creation is taking around 1 minute.

To avoid this much of delay we are exporting the maps into an image using SaveSvgAsPng.js library and once the image is created we are displaying the image on the app instead of creating the map every time the user logs into to the application (below is the code snippet from saveSvgAspng.js library)

Now with this approach we are seeing each time the image is exporting differently and there is drop in the image quality of the map (attached the image)

Raising this here to get some help in fixing this issue or if someone has faced this before as this is being the show stopper for our application. Happy to add more details if these are not sufficient.